* [PATCH v8 11/17] nfs: Implement fileattr_get for case sensitivity
From: Chuck Lever @ 2026-02-17 21:47 UTC (permalink / raw)
To: Al Viro, Christian Brauner, Jan Kara
Cc: linux-fsdevel, linux-ext4, linux-xfs, linux-cifs, linux-nfs,
linux-api, linux-f2fs-devel, hirofumi, linkinjeon, sj1557.seo,
yuezhang.mo, almaz.alexandrovich, slava, glaubitz, frank.li,
tytso, adilger.kernel, cem, sfrench, pc, ronniesahlberg, sprasad,
trondmy, anna, jaegeuk, chao, hansg, senozhatsky, Chuck Lever
In-Reply-To: <20260217214741.1928576-1-cel@kernel.org>
From: Chuck Lever <chuck.lever@oracle.com>
An NFS server re-exporting an NFS mount point needs to report the
case sensitivity behavior of the underlying filesystem to its
clients. Without this, re-export servers cannot accurately convey
case handling semantics, potentially causing client applications to
make incorrect assumptions about filename collisions and lookups.
The NFS client already retrieves case sensitivity information from
servers during mount via PATHCONF (NFSv3) or the
FATTR4_CASE_INSENSITIVE/FATTR4_CASE_PRESERVING attributes (NFSv4).
Expose this information through fileattr_get by reporting the
FS_XFLAG_CASEFOLD and FS_XFLAG_CASENONPRESERVING flags. NFSv2 lacks
PATHCONF support, so mounts using that protocol version default to
standard POSIX behavior: case-sensitive and case-preserving.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
fs/nfs/client.c | 9 +++++++--
fs/nfs/inode.c | 20 ++++++++++++++++++++
fs/nfs/internal.h | 3 +++
fs/nfs/nfs3proc.c | 2 ++
fs/nfs/nfs3xdr.c | 7 +++++--
fs/nfs/nfs4proc.c | 2 ++
fs/nfs/proc.c | 3 +++
fs/nfs/symlink.c | 3 +++
include/linux/nfs_xdr.h | 2 ++
9 files changed, 47 insertions(+), 4 deletions(-)
diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index fd15731cf361..0410f6053bfd 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -935,13 +935,18 @@ static int nfs_probe_fsinfo(struct nfs_server *server, struct nfs_fh *mntfh, str
/* Get some general file system info */
if (server->namelen == 0) {
- struct nfs_pathconf pathinfo;
+ struct nfs_pathconf pathinfo = { };
pathinfo.fattr = fattr;
nfs_fattr_init(fattr);
- if (clp->rpc_ops->pathconf(server, mntfh, &pathinfo) >= 0)
+ if (clp->rpc_ops->pathconf(server, mntfh, &pathinfo) >= 0) {
server->namelen = pathinfo.max_namelen;
+ if (pathinfo.case_insensitive)
+ server->caps |= NFS_CAP_CASE_INSENSITIVE;
+ if (pathinfo.case_preserving)
+ server->caps |= NFS_CAP_CASE_PRESERVING;
+ }
}
if (clp->rpc_ops->discover_trunking != NULL &&
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 331cdecdd966..8a2edce22a53 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -41,6 +41,7 @@
#include <linux/freezer.h>
#include <linux/uaccess.h>
#include <linux/iversion.h>
+#include <linux/fileattr.h>
#include "nfs4_fs.h"
#include "callback.h"
@@ -1101,6 +1102,25 @@ int nfs_getattr(struct mnt_idmap *idmap, const struct path *path,
}
EXPORT_SYMBOL_GPL(nfs_getattr);
+/**
+ * nfs_fileattr_get - Retrieve file attributes
+ * @dentry: object to query
+ * @fa: file attributes to fill in
+ *
+ * Return: 0 on success
+ */
+int nfs_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
+{
+ struct inode *inode = d_inode(dentry);
+
+ if (nfs_server_capable(inode, NFS_CAP_CASE_INSENSITIVE))
+ fa->fsx_xflags |= FS_XFLAG_CASEFOLD;
+ if (!nfs_server_capable(inode, NFS_CAP_CASE_PRESERVING))
+ fa->fsx_xflags |= FS_XFLAG_CASENONPRESERVING;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(nfs_fileattr_get);
+
static void nfs_init_lock_context(struct nfs_lock_context *l_ctx)
{
refcount_set(&l_ctx->count, 1);
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 63e09dfc27a8..e29695d4b7ed 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -449,6 +449,9 @@ extern void nfs_set_cache_invalid(struct inode *inode, unsigned long flags);
extern bool nfs_check_cache_invalid(struct inode *, unsigned long);
extern int nfs_wait_bit_killable(struct wait_bit_key *key, int mode);
+struct file_kattr;
+int nfs_fileattr_get(struct dentry *dentry, struct file_kattr *fa);
+
#if IS_ENABLED(CONFIG_NFS_LOCALIO)
/* localio.c */
struct nfs_local_dio {
diff --git a/fs/nfs/nfs3proc.c b/fs/nfs/nfs3proc.c
index d3d2fbeba89d..c30c8c6b1b9e 100644
--- a/fs/nfs/nfs3proc.c
+++ b/fs/nfs/nfs3proc.c
@@ -1047,6 +1047,7 @@ static const struct inode_operations nfs3_dir_inode_operations = {
.permission = nfs_permission,
.getattr = nfs_getattr,
.setattr = nfs_setattr,
+ .fileattr_get = nfs_fileattr_get,
#ifdef CONFIG_NFS_V3_ACL
.listxattr = nfs3_listxattr,
.get_inode_acl = nfs3_get_acl,
@@ -1058,6 +1059,7 @@ static const struct inode_operations nfs3_file_inode_operations = {
.permission = nfs_permission,
.getattr = nfs_getattr,
.setattr = nfs_setattr,
+ .fileattr_get = nfs_fileattr_get,
#ifdef CONFIG_NFS_V3_ACL
.listxattr = nfs3_listxattr,
.get_inode_acl = nfs3_get_acl,
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index e17d72908412..e745e78faab0 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -2276,8 +2276,11 @@ static int decode_pathconf3resok(struct xdr_stream *xdr,
if (unlikely(!p))
return -EIO;
result->max_link = be32_to_cpup(p++);
- result->max_namelen = be32_to_cpup(p);
- /* ignore remaining fields */
+ result->max_namelen = be32_to_cpup(p++);
+ p++; /* ignore no_trunc */
+ p++; /* ignore chown_restricted */
+ result->case_insensitive = be32_to_cpup(p++) != 0;
+ result->case_preserving = be32_to_cpup(p) != 0;
return 0;
}
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 180229320731..c9ab542bdb90 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -10598,6 +10598,7 @@ static const struct inode_operations nfs4_dir_inode_operations = {
.getattr = nfs_getattr,
.setattr = nfs_setattr,
.listxattr = nfs4_listxattr,
+ .fileattr_get = nfs_fileattr_get,
};
static const struct inode_operations nfs4_file_inode_operations = {
@@ -10605,6 +10606,7 @@ static const struct inode_operations nfs4_file_inode_operations = {
.getattr = nfs_getattr,
.setattr = nfs_setattr,
.listxattr = nfs4_listxattr,
+ .fileattr_get = nfs_fileattr_get,
};
static struct nfs_server *nfs4_clone_server(struct nfs_server *source,
diff --git a/fs/nfs/proc.c b/fs/nfs/proc.c
index 0e440ebf5335..a92c0ea26ea0 100644
--- a/fs/nfs/proc.c
+++ b/fs/nfs/proc.c
@@ -597,6 +597,7 @@ nfs_proc_pathconf(struct nfs_server *server, struct nfs_fh *fhandle,
{
info->max_link = 0;
info->max_namelen = NFS2_MAXNAMLEN;
+ info->case_preserving = true;
return 0;
}
@@ -717,12 +718,14 @@ static const struct inode_operations nfs_dir_inode_operations = {
.permission = nfs_permission,
.getattr = nfs_getattr,
.setattr = nfs_setattr,
+ .fileattr_get = nfs_fileattr_get,
};
static const struct inode_operations nfs_file_inode_operations = {
.permission = nfs_permission,
.getattr = nfs_getattr,
.setattr = nfs_setattr,
+ .fileattr_get = nfs_fileattr_get,
};
const struct nfs_rpc_ops nfs_v2_clientops = {
diff --git a/fs/nfs/symlink.c b/fs/nfs/symlink.c
index 58146e935402..74a072896f8d 100644
--- a/fs/nfs/symlink.c
+++ b/fs/nfs/symlink.c
@@ -22,6 +22,8 @@
#include <linux/mm.h>
#include <linux/string.h>
+#include "internal.h"
+
/* Symlink caching in the page cache is even more simplistic
* and straight-forward than readdir caching.
*/
@@ -74,4 +76,5 @@ const struct inode_operations nfs_symlink_inode_operations = {
.get_link = nfs_get_link,
.getattr = nfs_getattr,
.setattr = nfs_setattr,
+ .fileattr_get = nfs_fileattr_get,
};
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index ff1f12aa73d2..7c2057e40f99 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -182,6 +182,8 @@ struct nfs_pathconf {
struct nfs_fattr *fattr; /* Post-op attributes */
__u32 max_link; /* max # of hard links */
__u32 max_namelen; /* max name length */
+ bool case_insensitive;
+ bool case_preserving;
};
struct nfs4_change_info {
--
2.53.0
^ permalink raw reply related
* [PATCH v8 12/17] f2fs: Add case sensitivity reporting to fileattr_get
From: Chuck Lever @ 2026-02-17 21:47 UTC (permalink / raw)
To: Al Viro, Christian Brauner, Jan Kara
Cc: linux-fsdevel, linux-ext4, linux-xfs, linux-cifs, linux-nfs,
linux-api, linux-f2fs-devel, hirofumi, linkinjeon, sj1557.seo,
yuezhang.mo, almaz.alexandrovich, slava, glaubitz, frank.li,
tytso, adilger.kernel, cem, sfrench, pc, ronniesahlberg, sprasad,
trondmy, anna, jaegeuk, chao, hansg, senozhatsky, Chuck Lever
In-Reply-To: <20260217214741.1928576-1-cel@kernel.org>
From: Chuck Lever <chuck.lever@oracle.com>
NFS and other remote filesystem protocols need to determine
whether a local filesystem performs case-insensitive lookups
so they can provide correct semantics to clients. Without
this information, f2fs exports cannot properly advertise
their filename case behavior.
Report f2fs case sensitivity behavior via the FS_XFLAG_CASEFOLD
flag. Like ext4, f2fs supports per-directory case folding via
the casefold flag (IS_CASEFOLDED). Files are always case-preserving.
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
fs/f2fs/file.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index c8a2f17a8f11..f7f616e041dc 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -3453,6 +3453,13 @@ int f2fs_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
if (f2fs_sb_has_project_quota(F2FS_I_SB(inode)))
fa->fsx_projid = from_kprojid(&init_user_ns, fi->i_projid);
+ /*
+ * f2fs preserves case (the default). If this inode is a
+ * casefolded directory, report case-insensitive; otherwise
+ * report case-sensitive (standard POSIX behavior).
+ */
+ if (IS_CASEFOLDED(inode))
+ fa->fsx_xflags |= FS_XFLAG_CASEFOLD;
return 0;
}
--
2.53.0
^ permalink raw reply related
* [PATCH v8 13/17] vboxsf: Implement fileattr_get for case sensitivity
From: Chuck Lever @ 2026-02-17 21:47 UTC (permalink / raw)
To: Al Viro, Christian Brauner, Jan Kara
Cc: linux-fsdevel, linux-ext4, linux-xfs, linux-cifs, linux-nfs,
linux-api, linux-f2fs-devel, hirofumi, linkinjeon, sj1557.seo,
yuezhang.mo, almaz.alexandrovich, slava, glaubitz, frank.li,
tytso, adilger.kernel, cem, sfrench, pc, ronniesahlberg, sprasad,
trondmy, anna, jaegeuk, chao, hansg, senozhatsky, Chuck Lever
In-Reply-To: <20260217214741.1928576-1-cel@kernel.org>
From: Chuck Lever <chuck.lever@oracle.com>
Upper layers such as NFSD need a way to query whether a
filesystem handles filenames in a case-sensitive manner. Report
VirtualBox shared folder case handling behavior via the
FS_XFLAG_CASEFOLD flag.
The case sensitivity property is queried from the VirtualBox host
service at mount time and cached in struct vboxsf_sbi. The host
determines case sensitivity based on the underlying host filesystem
(for example, Windows NTFS is case-insensitive while Linux ext4 is
case-sensitive).
VirtualBox shared folders always preserve filename case exactly
as provided by the guest. The host interface does not expose a
case_preserving property, so this is hardcoded to true.
The callback is registered in all three inode_operations
structures (directory, file, and symlink) to ensure consistent
reporting across all inode types.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
fs/vboxsf/dir.c | 1 +
fs/vboxsf/file.c | 6 ++++--
fs/vboxsf/super.c | 4 ++++
fs/vboxsf/utils.c | 31 +++++++++++++++++++++++++++++++
fs/vboxsf/vfsmod.h | 6 ++++++
5 files changed, 46 insertions(+), 2 deletions(-)
diff --git a/fs/vboxsf/dir.c b/fs/vboxsf/dir.c
index 42bedc4ec7af..c5bd3271aa96 100644
--- a/fs/vboxsf/dir.c
+++ b/fs/vboxsf/dir.c
@@ -477,4 +477,5 @@ const struct inode_operations vboxsf_dir_iops = {
.symlink = vboxsf_dir_symlink,
.getattr = vboxsf_getattr,
.setattr = vboxsf_setattr,
+ .fileattr_get = vboxsf_fileattr_get,
};
diff --git a/fs/vboxsf/file.c b/fs/vboxsf/file.c
index 111752010edb..30a4f4262928 100644
--- a/fs/vboxsf/file.c
+++ b/fs/vboxsf/file.c
@@ -222,7 +222,8 @@ const struct file_operations vboxsf_reg_fops = {
const struct inode_operations vboxsf_reg_iops = {
.getattr = vboxsf_getattr,
- .setattr = vboxsf_setattr
+ .setattr = vboxsf_setattr,
+ .fileattr_get = vboxsf_fileattr_get,
};
static int vboxsf_read_folio(struct file *file, struct folio *folio)
@@ -389,5 +390,6 @@ static const char *vboxsf_get_link(struct dentry *dentry, struct inode *inode,
}
const struct inode_operations vboxsf_lnk_iops = {
- .get_link = vboxsf_get_link
+ .get_link = vboxsf_get_link,
+ .fileattr_get = vboxsf_fileattr_get,
};
diff --git a/fs/vboxsf/super.c b/fs/vboxsf/super.c
index 241647b060ee..fcabeca2a339 100644
--- a/fs/vboxsf/super.c
+++ b/fs/vboxsf/super.c
@@ -185,6 +185,10 @@ static int vboxsf_fill_super(struct super_block *sb, struct fs_context *fc)
if (err)
goto fail_unmap;
+ err = vboxsf_query_case_sensitive(sbi);
+ if (err)
+ goto fail_unmap;
+
sb->s_magic = VBOXSF_SUPER_MAGIC;
sb->s_blocksize = 1024;
sb->s_maxbytes = MAX_LFS_FILESIZE;
diff --git a/fs/vboxsf/utils.c b/fs/vboxsf/utils.c
index 9515bbf0b54c..658b8b0ebbd7 100644
--- a/fs/vboxsf/utils.c
+++ b/fs/vboxsf/utils.c
@@ -11,6 +11,7 @@
#include <linux/sizes.h>
#include <linux/pagemap.h>
#include <linux/vfs.h>
+#include <linux/fileattr.h>
#include "vfsmod.h"
struct inode *vboxsf_new_inode(struct super_block *sb)
@@ -567,3 +568,33 @@ int vboxsf_dir_read_all(struct vboxsf_sbi *sbi, struct vboxsf_dir_info *sf_d,
return err;
}
+
+int vboxsf_query_case_sensitive(struct vboxsf_sbi *sbi)
+{
+ struct shfl_volinfo volinfo = {};
+ u32 buf_len;
+ int err;
+
+ buf_len = sizeof(volinfo);
+ err = vboxsf_fsinfo(sbi->root, 0, SHFL_INFO_GET | SHFL_INFO_VOLUME,
+ &buf_len, &volinfo);
+ if (err)
+ return err;
+
+ sbi->case_insensitive = !volinfo.properties.case_sensitive;
+ return 0;
+}
+
+int vboxsf_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
+{
+ struct vboxsf_sbi *sbi = VBOXSF_SBI(dentry->d_sb);
+
+ /*
+ * VirtualBox shared folders preserve filename case exactly as
+ * provided by the guest (the default). The host interface does
+ * not expose a case-preservation property.
+ */
+ if (sbi->case_insensitive)
+ fa->fsx_xflags |= FS_XFLAG_CASEFOLD;
+ return 0;
+}
diff --git a/fs/vboxsf/vfsmod.h b/fs/vboxsf/vfsmod.h
index 05973eb89d52..b61afd0ce842 100644
--- a/fs/vboxsf/vfsmod.h
+++ b/fs/vboxsf/vfsmod.h
@@ -47,6 +47,7 @@ struct vboxsf_sbi {
u32 next_generation;
u32 root;
int bdi_id;
+ bool case_insensitive;
};
/* per-inode information */
@@ -111,6 +112,11 @@ void vboxsf_dir_info_free(struct vboxsf_dir_info *p);
int vboxsf_dir_read_all(struct vboxsf_sbi *sbi, struct vboxsf_dir_info *sf_d,
u64 handle);
+int vboxsf_query_case_sensitive(struct vboxsf_sbi *sbi);
+
+struct file_kattr;
+int vboxsf_fileattr_get(struct dentry *dentry, struct file_kattr *fa);
+
/* from vboxsf_wrappers.c */
int vboxsf_connect(void);
void vboxsf_disconnect(void);
--
2.53.0
^ permalink raw reply related
* [PATCH v8 14/17] isofs: Implement fileattr_get for case sensitivity
From: Chuck Lever @ 2026-02-17 21:47 UTC (permalink / raw)
To: Al Viro, Christian Brauner, Jan Kara
Cc: linux-fsdevel, linux-ext4, linux-xfs, linux-cifs, linux-nfs,
linux-api, linux-f2fs-devel, hirofumi, linkinjeon, sj1557.seo,
yuezhang.mo, almaz.alexandrovich, slava, glaubitz, frank.li,
tytso, adilger.kernel, cem, sfrench, pc, ronniesahlberg, sprasad,
trondmy, anna, jaegeuk, chao, hansg, senozhatsky, Chuck Lever
In-Reply-To: <20260217214741.1928576-1-cel@kernel.org>
From: Chuck Lever <chuck.lever@oracle.com>
Upper layers such as NFSD need a way to query whether a
filesystem handles filenames in a case-sensitive manner so
they can provide correct semantics to remote clients. Without
this information, NFS exports of ISO 9660 filesystems cannot
properly advertise their filename case behavior.
Implement isofs_fileattr_get() to report ISO 9660 case handling
behavior via the FS_XFLAG_CASEFOLD flag. The 'check=r' (relaxed)
mount option enables case-insensitive lookups, and this setting
determines the value reported. By default, Joliet extensions
operate in relaxed mode while plain ISO 9660 uses strict
(case-sensitive) mode. All ISO 9660 variants are case-preserving,
meaning filenames are stored exactly as they appear on the disc.
The callback is registered only on isofs_dir_inode_operations
because isofs has no custom inode_operations for regular
files, and symlinks use the generic page_symlink_inode_operations.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
fs/isofs/dir.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/fs/isofs/dir.c b/fs/isofs/dir.c
index 2ca16c3fe5ef..225124eefa46 100644
--- a/fs/isofs/dir.c
+++ b/fs/isofs/dir.c
@@ -14,6 +14,7 @@
#include <linux/gfp.h>
#include <linux/filelock.h>
#include "isofs.h"
+#include <linux/fileattr.h>
int isofs_name_translate(struct iso_directory_record *de, char *new, struct inode *inode)
{
@@ -267,6 +268,19 @@ static int isofs_readdir(struct file *file, struct dir_context *ctx)
return result;
}
+static int isofs_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
+{
+ struct isofs_sb_info *sbi = ISOFS_SB(dentry->d_sb);
+
+ /*
+ * FS_XFLAG_CASEFOLD indicates case-insensitive lookups.
+ * When check=r (relaxed) is set, lookups ignore case.
+ */
+ if (sbi->s_check == 'r')
+ fa->fsx_xflags |= FS_XFLAG_CASEFOLD;
+ return 0;
+}
+
const struct file_operations isofs_dir_operations =
{
.llseek = generic_file_llseek,
@@ -281,6 +295,7 @@ const struct file_operations isofs_dir_operations =
const struct inode_operations isofs_dir_inode_operations =
{
.lookup = isofs_lookup,
+ .fileattr_get = isofs_fileattr_get,
};
--
2.53.0
^ permalink raw reply related
* [PATCH v8 15/17] nfsd: Report export case-folding via NFSv3 PATHCONF
From: Chuck Lever @ 2026-02-17 21:47 UTC (permalink / raw)
To: Al Viro, Christian Brauner, Jan Kara
Cc: linux-fsdevel, linux-ext4, linux-xfs, linux-cifs, linux-nfs,
linux-api, linux-f2fs-devel, hirofumi, linkinjeon, sj1557.seo,
yuezhang.mo, almaz.alexandrovich, slava, glaubitz, frank.li,
tytso, adilger.kernel, cem, sfrench, pc, ronniesahlberg, sprasad,
trondmy, anna, jaegeuk, chao, hansg, senozhatsky, Chuck Lever
In-Reply-To: <20260217214741.1928576-1-cel@kernel.org>
From: Chuck Lever <chuck.lever@oracle.com>
The hard-coded MSDOS_SUPER_MAGIC check in nfsd3_proc_pathconf()
only recognizes FAT filesystems as case-insensitive. Modern
filesystems like F2FS, exFAT, and CIFS support case-insensitive
directories, but NFSv3 clients cannot discover this capability.
Query the export's actual case behavior through ->fileattr_get
instead. This allows NFSv3 clients to correctly handle case
sensitivity for any filesystem that implements the fileattr
interface. Filesystems without ->fileattr_get continue to report
the default POSIX behavior (case-sensitive, case-preserving).
This change assumes the ("fat: Implement fileattr_get for case
sensitivity") has been applied, which ensures FAT filesystems
report their case behavior correctly via the fileattr interface.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
fs/nfsd/nfs3proc.c | 18 ++++++++++--------
fs/nfsd/vfs.c | 25 +++++++++++++++++++++++++
fs/nfsd/vfs.h | 2 ++
3 files changed, 37 insertions(+), 8 deletions(-)
diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index 42adc5461db0..9be0aca01de0 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -717,17 +717,19 @@ nfsd3_proc_pathconf(struct svc_rqst *rqstp)
if (resp->status == nfs_ok) {
struct super_block *sb = argp->fh.fh_dentry->d_sb;
+ bool case_insensitive, case_preserving;
- /* Note that we don't care for remote fs's here */
- switch (sb->s_magic) {
- case EXT2_SUPER_MAGIC:
+ if (sb->s_magic == EXT2_SUPER_MAGIC) {
resp->p_link_max = EXT2_LINK_MAX;
resp->p_name_max = EXT2_NAME_LEN;
- break;
- case MSDOS_SUPER_MAGIC:
- resp->p_case_insensitive = 1;
- resp->p_case_preserving = 0;
- break;
+ }
+
+ resp->status = nfsd_get_case_info(&argp->fh,
+ &case_insensitive,
+ &case_preserving);
+ if (resp->status == nfs_ok) {
+ resp->p_case_insensitive = case_insensitive;
+ resp->p_case_preserving = case_preserving;
}
}
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index c884c3f34afb..75f862beb61f 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -32,6 +32,7 @@
#include <linux/writeback.h>
#include <linux/security.h>
#include <linux/sunrpc/xdr.h>
+#include <linux/fileattr.h>
#include "xdr3.h"
@@ -2891,3 +2892,27 @@ nfsd_permission(struct svc_cred *cred, struct svc_export *exp,
return err? nfserrno(err) : 0;
}
+
+/**
+ * nfsd_get_case_info - get case sensitivity info for a file handle
+ * @fhp: file handle that has already been verified
+ * @case_insensitive: output, true if the filesystem is case-insensitive
+ * @case_preserving: output, true if the filesystem preserves case
+ *
+ * Returns nfs_ok on success, or an nfserr on failure.
+ */
+__be32
+nfsd_get_case_info(struct svc_fh *fhp, bool *case_insensitive,
+ bool *case_preserving)
+{
+ struct file_kattr fa = {};
+ int err;
+
+ err = vfs_fileattr_get(fhp->fh_dentry, &fa);
+ if (err && err != -ENOIOCTLCMD)
+ return nfserrno(err);
+
+ *case_insensitive = fa.fsx_xflags & FS_XFLAG_CASEFOLD;
+ *case_preserving = !(fa.fsx_xflags & FS_XFLAG_CASENONPRESERVING);
+ return nfs_ok;
+}
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
index 702a844f2106..9425f2667d95 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -156,6 +156,8 @@ __be32 nfsd_readdir(struct svc_rqst *, struct svc_fh *,
loff_t *, struct readdir_cd *, nfsd_filldir_t);
__be32 nfsd_statfs(struct svc_rqst *, struct svc_fh *,
struct kstatfs *, int access);
+__be32 nfsd_get_case_info(struct svc_fh *fhp, bool *case_insensitive,
+ bool *case_preserving);
__be32 nfsd_permission(struct svc_cred *cred, struct svc_export *exp,
struct dentry *dentry, int acc);
--
2.53.0
^ permalink raw reply related
* [PATCH v8 16/17] nfsd: Implement NFSv4 FATTR4_CASE_INSENSITIVE and FATTR4_CASE_PRESERVING
From: Chuck Lever @ 2026-02-17 21:47 UTC (permalink / raw)
To: Al Viro, Christian Brauner, Jan Kara
Cc: linux-fsdevel, linux-ext4, linux-xfs, linux-cifs, linux-nfs,
linux-api, linux-f2fs-devel, hirofumi, linkinjeon, sj1557.seo,
yuezhang.mo, almaz.alexandrovich, slava, glaubitz, frank.li,
tytso, adilger.kernel, cem, sfrench, pc, ronniesahlberg, sprasad,
trondmy, anna, jaegeuk, chao, hansg, senozhatsky, Chuck Lever
In-Reply-To: <20260217214741.1928576-1-cel@kernel.org>
From: Chuck Lever <chuck.lever@oracle.com>
NFSD currently provides NFSv4 clients with hard-coded responses
indicating all exported filesystems are case-sensitive and
case-preserving. This is incorrect for case-insensitive filesystems
and ext4 directories with casefold enabled.
Query the underlying filesystem's actual case sensitivity via
nfsd_get_case_info() and return accurate values to clients. This
supports per-directory settings for filesystems that allow mixing
case-sensitive and case-insensitive directories within an export.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
fs/nfsd/nfs4xdr.c | 31 +++++++++++++++++++++++++++----
1 file changed, 27 insertions(+), 4 deletions(-)
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 5172dbd0cb05..26f77b622612 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3157,6 +3157,8 @@ struct nfsd4_fattr_args {
u32 rdattr_err;
bool contextsupport;
bool ignore_crossmnt;
+ bool case_insensitive;
+ bool case_preserving;
};
typedef __be32(*nfsd4_enc_attr)(struct xdr_stream *xdr,
@@ -3355,6 +3357,18 @@ static __be32 nfsd4_encode_fattr4_acl(struct xdr_stream *xdr,
return nfs_ok;
}
+static __be32 nfsd4_encode_fattr4_case_insensitive(struct xdr_stream *xdr,
+ const struct nfsd4_fattr_args *args)
+{
+ return nfsd4_encode_bool(xdr, args->case_insensitive);
+}
+
+static __be32 nfsd4_encode_fattr4_case_preserving(struct xdr_stream *xdr,
+ const struct nfsd4_fattr_args *args)
+{
+ return nfsd4_encode_bool(xdr, args->case_preserving);
+}
+
static __be32 nfsd4_encode_fattr4_filehandle(struct xdr_stream *xdr,
const struct nfsd4_fattr_args *args)
{
@@ -3747,8 +3761,8 @@ static const nfsd4_enc_attr nfsd4_enc_fattr4_encode_ops[] = {
[FATTR4_ACLSUPPORT] = nfsd4_encode_fattr4_aclsupport,
[FATTR4_ARCHIVE] = nfsd4_encode_fattr4__noop,
[FATTR4_CANSETTIME] = nfsd4_encode_fattr4__true,
- [FATTR4_CASE_INSENSITIVE] = nfsd4_encode_fattr4__false,
- [FATTR4_CASE_PRESERVING] = nfsd4_encode_fattr4__true,
+ [FATTR4_CASE_INSENSITIVE] = nfsd4_encode_fattr4_case_insensitive,
+ [FATTR4_CASE_PRESERVING] = nfsd4_encode_fattr4_case_preserving,
[FATTR4_CHOWN_RESTRICTED] = nfsd4_encode_fattr4__true,
[FATTR4_FILEHANDLE] = nfsd4_encode_fattr4_filehandle,
[FATTR4_FILEID] = nfsd4_encode_fattr4_fileid,
@@ -3954,8 +3968,9 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
if (err)
goto out_nfserr;
}
- if ((attrmask[0] & (FATTR4_WORD0_FILEHANDLE | FATTR4_WORD0_FSID)) &&
- !fhp) {
+ if ((attrmask[0] & (FATTR4_WORD0_FILEHANDLE | FATTR4_WORD0_FSID |
+ FATTR4_WORD0_CASE_INSENSITIVE |
+ FATTR4_WORD0_CASE_PRESERVING)) && !fhp) {
tempfh = kmalloc(sizeof(struct svc_fh), GFP_KERNEL);
status = nfserr_jukebox;
if (!tempfh)
@@ -3967,6 +3982,14 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
args.fhp = tempfh;
} else
args.fhp = fhp;
+ if (attrmask[0] & (FATTR4_WORD0_CASE_INSENSITIVE |
+ FATTR4_WORD0_CASE_PRESERVING)) {
+ status = nfsd_get_case_info(args.fhp, &args.case_insensitive,
+ &args.case_preserving);
+ if (status != nfs_ok)
+ attrmask[0] &= ~(FATTR4_WORD0_CASE_INSENSITIVE |
+ FATTR4_WORD0_CASE_PRESERVING);
+ }
if (attrmask[0] & FATTR4_WORD0_ACL) {
err = nfsd4_get_nfs4_acl(rqstp, dentry, &args.acl);
--
2.53.0
^ permalink raw reply related
* [PATCH v8 17/17] ksmbd: Report filesystem case sensitivity via FS_ATTRIBUTE_INFORMATION
From: Chuck Lever @ 2026-02-17 21:47 UTC (permalink / raw)
To: Al Viro, Christian Brauner, Jan Kara
Cc: linux-fsdevel, linux-ext4, linux-xfs, linux-cifs, linux-nfs,
linux-api, linux-f2fs-devel, hirofumi, linkinjeon, sj1557.seo,
yuezhang.mo, almaz.alexandrovich, slava, glaubitz, frank.li,
tytso, adilger.kernel, cem, sfrench, pc, ronniesahlberg, sprasad,
trondmy, anna, jaegeuk, chao, hansg, senozhatsky, Chuck Lever
In-Reply-To: <20260217214741.1928576-1-cel@kernel.org>
From: Chuck Lever <chuck.lever@oracle.com>
ksmbd hard-codes FILE_CASE_SENSITIVE_SEARCH and
FILE_CASE_PRESERVED_NAMES in FS_ATTRIBUTE_INFORMATION responses,
incorrectly indicating all exports are case-sensitive. This breaks
clients accessing case-insensitive filesystems like exFAT or
ext4/f2fs directories with casefold enabled.
Query actual case behavior via vfs_fileattr_get() and report accurate
attributes to SMB clients. Filesystems without ->fileattr_get continue
reporting default POSIX behavior (case-sensitive, case-preserving).
SMB's FS_ATTRIBUTE_INFORMATION reports per-share attributes from the
share root, not per-file. Shares mixing casefold and non-casefold
directories report the root directory's behavior.
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
fs/smb/server/smb2pdu.c | 25 +++++++++++++++++++------
1 file changed, 19 insertions(+), 6 deletions(-)
diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index cbb31efdbaa2..d2a64afdd950 100644
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -13,6 +13,7 @@
#include <linux/falloc.h>
#include <linux/mount.h>
#include <linux/filelock.h>
+#include <linux/fileattr.h>
#include "glob.h"
#include "smbfsctl.h"
@@ -5497,16 +5498,28 @@ static int smb2_get_info_filesystem(struct ksmbd_work *work,
case FS_ATTRIBUTE_INFORMATION:
{
FILE_SYSTEM_ATTRIBUTE_INFO *info;
+ struct file_kattr fa = {};
size_t sz;
+ u32 attrs;
+ int err;
info = (FILE_SYSTEM_ATTRIBUTE_INFO *)rsp->Buffer;
- info->Attributes = cpu_to_le32(FILE_SUPPORTS_OBJECT_IDS |
- FILE_PERSISTENT_ACLS |
- FILE_UNICODE_ON_DISK |
- FILE_CASE_PRESERVED_NAMES |
- FILE_CASE_SENSITIVE_SEARCH |
- FILE_SUPPORTS_BLOCK_REFCOUNTING);
+ attrs = FILE_SUPPORTS_OBJECT_IDS |
+ FILE_PERSISTENT_ACLS |
+ FILE_UNICODE_ON_DISK |
+ FILE_SUPPORTS_BLOCK_REFCOUNTING;
+ err = vfs_fileattr_get(path.dentry, &fa);
+ if (err && err != -ENOIOCTLCMD) {
+ path_put(&path);
+ return err;
+ }
+ if (!(fa.fsx_xflags & FS_XFLAG_CASEFOLD))
+ attrs |= FILE_CASE_SENSITIVE_SEARCH;
+ if (!(fa.fsx_xflags & FS_XFLAG_CASENONPRESERVING))
+ attrs |= FILE_CASE_PRESERVED_NAMES;
+
+ info->Attributes = cpu_to_le32(attrs);
info->Attributes |= cpu_to_le32(server_conf.share_fake_fscaps);
if (test_share_config_flag(work->tcon->share_conf,
--
2.53.0
^ permalink raw reply related
* Re: [PATCH bpf-next v10 4/8] bpf: Add syscall common attributes support for prog_load
From: Andrii Nakryiko @ 2026-02-18 18:44 UTC (permalink / raw)
To: Leon Hwang
Cc: bpf, Alexei Starovoitov, Daniel Borkmann, John Fastabend,
Andrii Nakryiko, Martin KaFai Lau, Eduard Zingerman, Song Liu,
Yonghong Song, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa,
Shuah Khan, Christian Brauner, Seth Forshee, Yuichiro Tsuji,
Andrey Albershteyn, Willem de Bruijn, Jason Xing, Tao Chen,
Mykyta Yatsenko, Kumar Kartikeya Dwivedi, Anton Protopopov,
Amery Hung, Rong Tao, linux-kernel, linux-api, linux-kselftest,
kernel-patches-bot
In-Reply-To: <eb82cc40-e5c0-4f23-ad92-92633ccb2e0d@linux.dev>
On Wed, Feb 11, 2026 at 9:50 PM Leon Hwang <leon.hwang@linux.dev> wrote:
>
>
>
> On 12/2/26 06:08, Andrii Nakryiko wrote:
> > On Wed, Feb 11, 2026 at 7:13 AM Leon Hwang <leon.hwang@linux.dev> wrote:
> >>
>
> [...]
>
> >> diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
> >> index e31747b84fe2..a2b41bf5e9cb 100644
> >> --- a/kernel/bpf/log.c
> >> +++ b/kernel/bpf/log.c
> >> @@ -864,14 +864,43 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
> >> print_verifier_state(env, vstate, frameno, false);
> >> }
> >>
> >> +static bool bpf_log_attrs_set(u64 log_buf, u32 log_size, u32 log_level)
> >> +{
> >> + return log_buf && log_size && log_level;
> >> +}
> >> +
> >> +static bool bpf_log_attrs_diff(struct bpf_common_attr *common, u64 log_buf, u32 log_size,
> >> + u32 log_level)
> >> +{
> >> + return bpf_log_attrs_set(log_buf, log_size, log_level) &&
> >> + bpf_log_attrs_set(common->log_buf, common->log_size, common->log_level) &&
> >> + (log_buf != common->log_buf || log_size != common->log_size ||
> >> + log_level != common->log_level);
> >> +}
> >> +
> >
> > I'm not sure this check is doing what we discussed previously?... If
> > log_buf is set, but log_size or log_level is zero, you'll just ignore
> > log_buf here...
> >
> > Maybe let's keep it super simple:
> >
> > if (log_buf && common->log_buf && log_buf != common->log_buf)
> > return -EINVAL;
> > /* same for log_size, log_level, log_true_size */
> >
> > and then below just
> >
> > log->log_buf = u64_to_user_ptr(log_buf ?: common->log_buf);
> > log->log_size = log_size ?: common->log_size;
> >
> > and so on
> >
> >
> > We can be stricter than that, of course (as in, all triplets have to
> > be completely set in either/both common_attr and attr, and they should
> > completely match), but it's just more code for little benefit.
> >
>
> We cannot mix fields across the two sources. For example, using log_buf
> from attr together with common->log_size when log_size is zero would mix
> the configuration and make the effective log setup ambiguous.
>
> The intent is to align strictly with the semantics enforced by
> bpf_verifier_log_attr_valid():
>
> * log_buf and log_size must be specified together.
> * A non-NULL log_buf requires log_level != 0.
> * All values must pass basic sanity checks.
>
> Given that contract, we should:
>
> 1. Validate the log attributes from attr and common independently using
> the same helper.
> 2. if both sides provide log buffers, require the tuples to match
> exactly.
> 3. select either the attr tuple or the common tuple as a whole — never
> mix fields across the two.
>
> The patch below implements this by reusing bpf_verifier_log_attr_valid()
> for both sources and resolving conflicts before selecting the effective
> log configuration.
> >
> >> int bpf_log_attr_init(struct bpf_log_attr *log, u64 log_buf, u32 log_size, u32 log_level,
> >> - u32 __user *log_true_size)
> >> + u32 __user *log_true_size, struct bpf_common_attr *common, bpfptr_t uattr,
> >> + u32 size)
> >> {
> >> + if (bpf_log_attrs_diff(common, log_buf, log_size, log_level))
> >> + return -EINVAL;
> >> +
> >> memset(log, 0, sizeof(*log));
> >> log->log_buf = u64_to_user_ptr(log_buf);
> >> log->log_size = log_size;
> >> log->log_level = log_level;
> >> log->log_true_size = log_true_size;
> >> +
> >> + if (!log_buf && common->log_buf) {
> >> + log->log_buf = u64_to_user_ptr(common->log_buf);
> >> + log->log_size = common->log_size;
> >> + log->log_level = common->log_level;
> >> + if (size >= offsetofend(struct bpf_common_attr, log_true_size))
> >> + log->log_true_size = uattr.user +
> >> + offsetof(struct bpf_common_attr, log_true_size);
> >> + else
> >> + log->log_true_size = NULL;
> >
> > why not treat log_true_size same as log_buf/log_level/log_size? If
> > both are provided, they should match, and then we don't have a
> > possibility of inconsistency?
> >
> log_true_size is different from log_buf/log_size/log_level.
>
> It is not a regular attribute stored in either union bpf_attr or
> struct bpf_common_attr. Instead, it is a user pointer derived from
> uattr.user + offset.
>
> As a result, the computed log_true_size pointer for union bpf_attr
> and for struct bpf_common_attr will always differ, because they are
> based on different base user pointers (uattr.user vs
> uattr_common.user).
>
> So unlike the other log attributes, pointer equality is not a
> meaningful consistency check for log_true_size. The only sensible
> rule is that whichever side provides the effective log triplet also
> determines the write-back destination.
yeah, you are right, I forgot that log_true_size is not a pointer
itself, it's just a field in user-provided attrs. I'll check what you
did in v11, let's continue there.
>
> Thanks,
> Leon
>
> ---
>
> Based-on commit 19de32d4cb58 ("selftests/bpf: Migrate align.c tests to
> test_loader framework").
>
> From 32ec02c06d2abacbde17a45edbda46ef8a16fa2d Mon Sep 17 00:00:00 2001
> From: Leon Hwang <leon.hwang@linux.dev>
> Date: Wed, 11 Feb 2026 23:11:11 +0800
> Subject: [PATCH bpf-next v11 4/8] bpf: Add syscall common attributes support
> for prog_load
>
> BPF_PROG_LOAD can now take log parameters from both union bpf_attr and
> struct bpf_common_attr. The merge rules are:
>
> - if both sides provide a complete log tuple (buf/size/level) and they
> match, use it;
> - if only one side provides log parameters, use that one;
> - if both sides provide complete tuples but they differ, return -EINVAL.
>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
> include/linux/bpf_verifier.h | 3 ++-
> kernel/bpf/log.c | 38 ++++++++++++++++++++++++++++--------
> kernel/bpf/syscall.c | 2 +-
> 3 files changed, 33 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index dbd9bdb955b3..34f28d40022a 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -643,7 +643,8 @@ struct bpf_log_attr {
> };
>
> int bpf_log_attr_init(struct bpf_log_attr *log, u64 log_buf, u32
> log_size, u32 log_level,
> - u32 __user *log_true_size);
> + u32 __user *log_true_size, struct bpf_common_attr *common,
> bpfptr_t uattr,
> + u32 size);
> int bpf_log_attr_finalize(struct bpf_log_attr *attr, struct
> bpf_verifier_log *log);
>
> #define BPF_MAX_SUBPROGS 256
> diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
> index e31747b84fe2..47bf496b673e 100644
> --- a/kernel/bpf/log.c
> +++ b/kernel/bpf/log.c
> @@ -13,17 +13,17 @@
>
> #define verbose(env, fmt, args...) bpf_verifier_log_write(env, fmt, ##args)
>
> -static bool bpf_verifier_log_attr_valid(const struct bpf_verifier_log *log)
> +static bool bpf_verifier_log_attr_valid(u32 log_level, char __user
> *log_buf, u32 log_size)
> {
> /* ubuf and len_total should both be specified (or not) together */
> - if (!!log->ubuf != !!log->len_total)
> + if (!!log_buf != !!log_size)
> return false;
> /* log buf without log_level is meaningless */
> - if (log->ubuf && log->level == 0)
> + if (log_buf && log_level == 0)
> return false;
> - if (log->level & ~BPF_LOG_MASK)
> + if (log_level & ~BPF_LOG_MASK)
> return false;
> - if (log->len_total > UINT_MAX >> 2)
> + if (log_size > UINT_MAX >> 2)
> return false;
> return true;
> }
> @@ -36,7 +36,7 @@ int bpf_vlog_init(struct bpf_verifier_log *log, u32
> log_level,
> log->len_total = log_size;
>
> /* log attributes have to be sane */
> - if (!bpf_verifier_log_attr_valid(log))
> + if (!bpf_verifier_log_attr_valid(log_level, log_buf, log_size))
> return -EINVAL;
>
> return 0;
> @@ -865,13 +865,35 @@ void print_insn_state(struct bpf_verifier_env
> *env, const struct bpf_verifier_st
> }
>
> int bpf_log_attr_init(struct bpf_log_attr *log, u64 log_buf, u32
> log_size, u32 log_level,
> - u32 __user *log_true_size)
> + u32 __user *log_true_size, struct bpf_common_attr *common,
> bpfptr_t uattr,
> + u32 size)
> {
> + char __user *ubuf_common = u64_to_user_ptr(common->log_buf);
> + char __user *ubuf = u64_to_user_ptr(log_buf);
> +
> + if (!bpf_verifier_log_attr_valid(common->log_level, ubuf_common,
> common->log_size) ||
> + !bpf_verifier_log_attr_valid(log_level, ubuf, log_size))
> + return -EINVAL;
> +
> + if (ubuf && ubuf_common && (ubuf != ubuf_common || log_size !=
> common->log_size ||
> + log_level != common->log_level))
> + return -EINVAL;
> +
> memset(log, 0, sizeof(*log));
> - log->log_buf = u64_to_user_ptr(log_buf);
> + log->log_buf = ubuf;
> log->log_size = log_size;
> log->log_level = log_level;
> log->log_true_size = log_true_size;
> +
> + if (!ubuf && ubuf_common) {
> + log->log_buf = ubuf_common;
> + log->log_size = common->log_size;
> + log->log_level = common->log_level;
> + log->log_true_size = NULL;
> + if (size >= offsetofend(struct bpf_common_attr, log_true_size))
> + log->log_true_size = uattr.user +
> + offsetof(struct bpf_common_attr, log_true_size);
> + }
> return 0;
> }
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index e86674811996..17116603ff51 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -6247,7 +6247,7 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t
> uattr, unsigned int size,
> if (from_user && size >= offsetofend(union bpf_attr, log_true_size))
> log_true_size = uattr.user + offsetof(union bpf_attr, log_true_size);
> err = bpf_log_attr_init(&attr_log, attr.log_buf, attr.log_size,
> attr.log_level,
> - log_true_size);
> + log_true_size, &attr_common, uattr_common, size_common);
> err = err ?: bpf_prog_load(&attr, uattr, &attr_log);
> break;
> case BPF_OBJ_PIN:
> --
> 2.52.0
>
>
^ permalink raw reply
* Re: [PATCH v8 08/17] ext4: Report case sensitivity in fileattr_get
From: Theodore Tso @ 2026-02-19 13:14 UTC (permalink / raw)
To: Chuck Lever
Cc: Al Viro, Christian Brauner, Jan Kara, linux-fsdevel, linux-ext4,
linux-xfs, linux-cifs, linux-nfs, linux-api, linux-f2fs-devel,
hirofumi, linkinjeon, sj1557.seo, yuezhang.mo,
almaz.alexandrovich, slava, glaubitz, frank.li, adilger.kernel,
cem, sfrench, pc, ronniesahlberg, sprasad, trondmy, anna, jaegeuk,
chao, hansg, senozhatsky, Chuck Lever
In-Reply-To: <20260217214741.1928576-9-cel@kernel.org>
On Tue, Feb 17, 2026 at 04:47:32PM -0500, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
>
> Report ext4's case sensitivity behavior via the FS_XFLAG_CASEFOLD
> flag. ext4 always preserves case at rest.
>
> Case sensitivity is a per-directory setting in ext4. If the queried
> inode is a casefolded directory, report case-insensitive; otherwise
> report case-sensitive (standard POSIX behavior).
>
> Reviewed-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Acked-by: Theodore Ts'o <tytso@mit.edu>
^ permalink raw reply
* Re: [PATCH 0/2] mount: add OPEN_TREE_NAMESPACE
From: Askar Safin @ 2026-02-19 23:42 UTC (permalink / raw)
To: rob; +Cc: containers, initramfs, linux-api, linux-fsdevel, linux-kernel
In-Reply-To: <6375f293-709c-41b8-a23d-12010baa3cae@landley.net>
Rob Landley <rob@landley.net>:
> Also, could you guys make CONFIG_DEVTMPFS_MOUNT work with initramfs?
I did something similar:
https://lore.kernel.org/initramfs/20260219210312.3468980-1-safinaskar@gmail.com/T/#u
Does this solve your problem?
--
Askar Safin
^ permalink raw reply
* [RFC PATCH 1/2] futex: Create reproducer for robust_list race condition
From: André Almeida @ 2026-02-20 20:26 UTC (permalink / raw)
To: Carlos O'Donell, Sebastian Andrzej Siewior, Peter Zijlstra,
Florian Weimer, Rich Felker, Torvald Riegel, Darren Hart,
Thomas Gleixner, Ingo Molnar, Davidlohr Bueso, Arnd Bergmann,
Mathieu Desnoyers, Liam R . Howlett
Cc: kernel-dev, linux-api, linux-kernel, André Almeida
In-Reply-To: <20260220202620.139584-1-andrealmeid@igalia.com>
Create a reproducer for https://sourceware.org/bugzilla/show_bug.cgi?id=14485
This is not supposed to be merged.
Signed-off-by: André Almeida <andrealmeid@igalia.com>
---
robust_bug.c | 178 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 178 insertions(+)
create mode 100644 robust_bug.c
diff --git a/robust_bug.c b/robust_bug.c
new file mode 100644
index 000000000000..1ade4e6d66dd
--- /dev/null
+++ b/robust_bug.c
@@ -0,0 +1,178 @@
+/*
+ * gcc robust_bug.c -o robust_bug
+ *
+ * This is a reproducer for "File corruption race condition in robust
+ * mutex unlocking" from https://sourceware.org/bugzilla/show_bug.cgi?id=14485
+ *
+ * To increase the changes of reaching the race condition, a delay can be added
+ * to the kernel function handle_futex_death(), just before the user memory
+ * write futex_cmpxchg_value_locked().
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <linux/futex.h>
+#include <pthread.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <time.h>
+
+#define cpu_relax() asm volatile("rep; nop");
+
+/*
+ * This struct is an example of a lock struct, shared between the threads.
+ */
+struct lock_struct {
+ uint32_t futex;
+ struct robust_list list;
+};
+
+static struct lock_struct *lock;
+
+/*
+ * This is the struct that we are going to use to allocate on top of the
+ * freed memory to observe the race condition.
+ */
+struct another_struct {
+ uint64_t value;
+};
+
+static pthread_barrier_t barrier;
+
+static int set_robust_list(struct robust_list_head *head)
+{
+ return syscall(SYS_set_robust_list, head, sizeof(*head));
+}
+
+/*
+ * This thread emulates the behaviour of a thread releasing a robust mutex:
+ * - It starts by adding the mutex to the op_pending field
+ * - Remove the mutex from the robust list
+ * - Release the lock and wake up waiters
+ * - Remove the mutex from the op_pending field
+ *
+ * However, this thread dies before doing this last step, leaving the mutex
+ * behind in the op_pending field.
+ */
+void *func_b(void *arg)
+{
+ static struct robust_list_head head;
+ pid_t tid = gettid() | FUTEX_WAITERS;
+
+ /*
+ * Initial thread setup. This would happen in an earlier stage of the
+ * thread execution.
+ */
+ set_robust_list(&head);
+ head.list.next = &head.list;
+ head.futex_offset = (size_t) offsetof(struct lock_struct, futex) -
+ (size_t) offsetof(struct lock_struct, list);
+
+ /* This thread takes the lock... */
+ lock->futex = tid;
+
+ /* ...would do some work here... */
+
+ /*
+ * ...and starts the release process. Adds the mutex to be released on
+ * the op_pending.
+ */
+ head.list_op_pending = &lock->list;
+
+ /* Barrier to synchronize thread B taking the lock */
+ pthread_barrier_wait(&barrier);
+ usleep(100);
+
+ /*
+ * Here we would release the lock and wake up any waiters.
+ *
+ * lock->futex = LOCK_FREE;
+ * futex_wake(lock->futex, 1);
+ */
+
+ /*
+ * We would remove the lock from op_pending, but we emulate a thread
+ * exiting before doing it.
+ */
+ return NULL;
+}
+
+int main(int argc, char *argv[])
+{
+ struct another_struct *new;
+ uint64_t original_val;
+ pthread_t thread_b;
+ uint32_t value;
+ int ret;
+
+ ret = pthread_barrier_init(&barrier, NULL, 2);
+ if (ret) {
+ puts("pthread_barrier_init failed");
+ return -1;
+ }
+
+ /* Initialize the lock */
+ lock = mmap(NULL, sizeof(struct lock_struct), PROT_READ | PROT_WRITE,
+ MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+ if (lock == MAP_FAILED) {
+ puts("mmap failed");
+ return -1;
+ }
+ memset(lock, 0, sizeof(*lock));
+
+ /* Create the thread B that will take the lock */
+ pthread_create(&thread_b, NULL, func_b, NULL);
+
+ /* Barrier to synchronize thread B taking the lock */
+ pthread_barrier_wait(&barrier);
+
+ /* Copy this value as we will use it later */
+ value = lock->futex;
+
+ /*
+ * Here, this thread would do the following:
+ * - It would wait for the lock, and be wake from thread B
+ * - Take the lock, do some work, and release it
+ * - After releasing the lock and being the last user, it can correctly
+ * free it
+ */
+ munmap(lock, sizeof(struct lock_struct));
+
+ /*
+ * After freeing the lock, this thread allocates memory, which
+ * happens to be at the same address of the lock, and by chance, it fills
+ * the memory with the TID of thread B.
+ */
+ new = mmap(NULL, sizeof(struct another_struct), PROT_READ | PROT_WRITE,
+ MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+ if (new == MAP_FAILED) {
+ puts("mmap failed");
+ return -1;
+ }
+ if ((uintptr_t) lock != (uintptr_t) new) {
+ puts("mmap got a different address");
+ return -1;
+ }
+
+ new->value = ((uint64_t) value << 32) + value;
+
+ /* Create a backup of the current value */
+ original_val = new->value;
+
+ /* Wait for the memory corruption to happen... */
+ while (new->value == original_val)
+ cpu_relax();
+
+ /* ...and now the kernel just overwrote an unrelated user memory! */
+ printf("Memory was corrupted by the kernel: %lx vs %lx\n",
+ original_val, new->value);
+
+ munmap(new, sizeof(struct another_struct));
+
+ return 0;
+}
--
2.53.0
^ permalink raw reply related
* [RFC PATCH 2/2] futex: hack: Add debug delays
From: André Almeida @ 2026-02-20 20:26 UTC (permalink / raw)
To: Carlos O'Donell, Sebastian Andrzej Siewior, Peter Zijlstra,
Florian Weimer, Rich Felker, Torvald Riegel, Darren Hart,
Thomas Gleixner, Ingo Molnar, Davidlohr Bueso, Arnd Bergmann,
Mathieu Desnoyers, Liam R . Howlett
Cc: kernel-dev, linux-api, linux-kernel, André Almeida
In-Reply-To: <20260220202620.139584-1-andrealmeid@igalia.com>
Add delays to handle_futex_death() to increase the chance of hitting the race
condition.
Signed-off-by: André Almeida <andrealmeid@igalia.com>
---
kernel/futex/core.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/kernel/futex/core.c b/kernel/futex/core.c
index cf7e610eac42..d409b3368cb3 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -44,6 +44,7 @@
#include <linux/prctl.h>
#include <linux/mempolicy.h>
#include <linux/mmap_lock.h>
+#include <linux/delay.h>
#include "futex.h"
#include "../locking/rtmutex_common.h"
@@ -1095,6 +1096,12 @@ static int handle_futex_death(u32 __user *uaddr, struct task_struct *curr,
* does not guarantee R/W access. If that fails we
* give up and leave the futex locked.
*/
+
+ if (!strcmp(current->comm, "robust_bug")) {
+ printk("robust_bug is exiting\n");
+ msleep(500);
+ }
+
if ((err = futex_cmpxchg_value_locked(&nval, uaddr, uval, mval))) {
switch (err) {
case -EFAULT:
@@ -1112,6 +1119,9 @@ static int handle_futex_death(u32 __user *uaddr, struct task_struct *curr,
}
}
+ if (!strcmp(current->comm, "robust_bug"))
+ printk("memory written\n");
+
if (nval != uval)
goto retry;
--
2.53.0
^ permalink raw reply related
* [RFC PATCH 0/2] futex: how to solve the robust_list race condition?
From: André Almeida @ 2026-02-20 20:26 UTC (permalink / raw)
To: Carlos O'Donell, Sebastian Andrzej Siewior, Peter Zijlstra,
Florian Weimer, Rich Felker, Torvald Riegel, Darren Hart,
Thomas Gleixner, Ingo Molnar, Davidlohr Bueso, Arnd Bergmann,
Mathieu Desnoyers, Liam R . Howlett
Cc: kernel-dev, linux-api, linux-kernel, André Almeida
During LPC 2025, I presented a session about creating a new syscall for
robust_list[0][1]. However, most of the session discussion wasn't much related
to the new syscall itself, but much more related to an old bug that exists in
the current robust_list mechanism.
Since at least 2012, there's an open bug reporting a race condition, as
Carlos O'Donell pointed out:
"File corruption race condition in robust mutex unlocking"
https://sourceware.org/bugzilla/show_bug.cgi?id=14485
To help understand the bug, I've created a reproducer (patch 1/2) and a
companion kernel hack (patch 2/2) that helps to make the race condition
more likely. When the bug happens, the reproducer shows a message
comparing the original memory with the corrupted one:
"Memory was corrupted by the kernel: 8001fe8d8001fe8d vs 8001fe8dc0000000"
I'm not sure yet what would be the appropriated approach to fix it, so I
decided to reach the community before moving forward in some direction.
One suggestion from Peter[2] resolves around serializing the mmap() and the
robust list exit path, which might cause overheads for the common case,
where list_op_pending is empty.
However, giving that there's a new interface being prepared, this could
also give the opportunity to rethink how list_op_pending works, and get
rid of the race condition by design.
Feedback is very much welcome.
Thanks!
André
[0] https://lore.kernel.org/lkml/20251122-tonyk-robust_futex-v6-0-05fea005a0fd@igalia.com/
[1] https://lpc.events/event/19/contributions/2108/
[2] https://lore.kernel.org/lkml/20241219171344.GA26279@noisy.programming.kicks-ass.net/
André Almeida (2):
futex: Create reproducer for robust_list race condition
futex: Add debug delays
kernel/futex/core.c | 10 +++
robust_bug.c | 178 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 188 insertions(+)
create mode 100644 robust_bug.c
--
2.53.0
^ permalink raw reply
* Re: [RFC PATCH 0/2] futex: how to solve the robust_list race condition?
From: Liam R. Howlett @ 2026-02-20 20:51 UTC (permalink / raw)
To: André Almeida
Cc: Carlos O'Donell, Sebastian Andrzej Siewior, Peter Zijlstra,
Florian Weimer, Rich Felker, Torvald Riegel, Darren Hart,
Thomas Gleixner, Ingo Molnar, Davidlohr Bueso, Arnd Bergmann,
Mathieu Desnoyers, kernel-dev, linux-api, linux-kernel,
Suren Baghdasaryan, Lorenzo Stoakes, Michal Hocko
In-Reply-To: <20260220202620.139584-1-andrealmeid@igalia.com>
+Cc Suren, Lorenzo, and Michal
* André Almeida <andrealmeid@igalia.com> [260220 15:27]:
> During LPC 2025, I presented a session about creating a new syscall for
> robust_list[0][1]. However, most of the session discussion wasn't much related
> to the new syscall itself, but much more related to an old bug that exists in
> the current robust_list mechanism.
Ah, sorry for hijacking the session, that was not my intention, but this
needs to be addressed before we propagate the issue into the next
iteration.
>
> Since at least 2012, there's an open bug reporting a race condition, as
> Carlos O'Donell pointed out:
>
> "File corruption race condition in robust mutex unlocking"
> https://sourceware.org/bugzilla/show_bug.cgi?id=14485
>
> To help understand the bug, I've created a reproducer (patch 1/2) and a
> companion kernel hack (patch 2/2) that helps to make the race condition
> more likely. When the bug happens, the reproducer shows a message
> comparing the original memory with the corrupted one:
>
> "Memory was corrupted by the kernel: 8001fe8d8001fe8d vs 8001fe8dc0000000"
>
> I'm not sure yet what would be the appropriated approach to fix it, so I
> decided to reach the community before moving forward in some direction.
> One suggestion from Peter[2] resolves around serializing the mmap() and the
> robust list exit path, which might cause overheads for the common case,
> where list_op_pending is empty.
>
> However, giving that there's a new interface being prepared, this could
> also give the opportunity to rethink how list_op_pending works, and get
> rid of the race condition by design.
>
> Feedback is very much welcome.
There was a delay added to the oom reaper for these tasks [1] by commit
e4a38402c36e ("oom_kill.c: futex: delay the OOM reaper to allow time for
proper futex cleanup")
We did discuss marking the vmas as needing to be skipped by the oom
manager, but no clear path forward was clear. It's also not clear if
that's the only area where such a problem exists.
[1]. https://lore.kernel.org/all/20220414144042.677008-1-npache@redhat.com/T/#u
>
> Thanks!
> André
>
> [0] https://lore.kernel.org/lkml/20251122-tonyk-robust_futex-v6-0-05fea005a0fd@igalia.com/
> [1] https://lpc.events/event/19/contributions/2108/
> [2] https://lore.kernel.org/lkml/20241219171344.GA26279@noisy.programming.kicks-ass.net/
>
> André Almeida (2):
> futex: Create reproducer for robust_list race condition
> futex: Add debug delays
>
> kernel/futex/core.c | 10 +++
> robust_bug.c | 178 ++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 188 insertions(+)
> create mode 100644 robust_bug.c
>
> --
> 2.53.0
>
^ permalink raw reply
* Re: [RFC PATCH 0/2] futex: how to solve the robust_list race condition?
From: Mathieu Desnoyers @ 2026-02-20 21:42 UTC (permalink / raw)
To: André Almeida, Carlos O'Donell,
Sebastian Andrzej Siewior, Peter Zijlstra, Florian Weimer,
Rich Felker, Torvald Riegel, Darren Hart, Thomas Gleixner,
Ingo Molnar, Davidlohr Bueso, Arnd Bergmann, Liam R . Howlett,
Lorenzo Stoakes, Michal Hocko
Cc: kernel-dev, linux-api, linux-kernel, libc-alpha
In-Reply-To: <20260220202620.139584-1-andrealmeid@igalia.com>
+CC libc-alpha.
On 2026-02-20 15:26, André Almeida wrote:
> During LPC 2025, I presented a session about creating a new syscall for
> robust_list[0][1]. However, most of the session discussion wasn't much related
> to the new syscall itself, but much more related to an old bug that exists in
> the current robust_list mechanism.
>
> Since at least 2012, there's an open bug reporting a race condition, as
> Carlos O'Donell pointed out:
>
> "File corruption race condition in robust mutex unlocking"
> https://sourceware.org/bugzilla/show_bug.cgi?id=14485
>
> To help understand the bug, I've created a reproducer (patch 1/2) and a
> companion kernel hack (patch 2/2) that helps to make the race condition
> more likely. When the bug happens, the reproducer shows a message
> comparing the original memory with the corrupted one:
>
> "Memory was corrupted by the kernel: 8001fe8d8001fe8d vs 8001fe8dc0000000"
>
> I'm not sure yet what would be the appropriated approach to fix it, so I
> decided to reach the community before moving forward in some direction.
> One suggestion from Peter[2] resolves around serializing the mmap() and the
> robust list exit path, which might cause overheads for the common case,
> where list_op_pending is empty.
>
> However, giving that there's a new interface being prepared, this could
> also give the opportunity to rethink how list_op_pending works, and get
> rid of the race condition by design.
>
> Feedback is very much welcome.
Looking at this bug, one thing I'm starting to consider is that it
appears to be an issue inherent to lack of synchronization between
pthread_mutex_destroy(3) and the per-thread list_op_pending fields
and not so much a kernel issue.
Here is why I think the issue is purely userspace:
Let's suppose we have a shared memory area across Processes 1 and Process 2,
which internally have its own custom memory allocator in userspace to
allocate/free space within that shared memory.
Process 1, Thread A stumbles through the scenario highlighted by this bug, and
basically gets preempted at this FIXME in libc __pthread_mutex_unlock_full():
if (__glibc_unlikely ((atomic_exchange_release (&mutex->__data.__lock, 0)
& FUTEX_WAITERS) != 0))
futex_wake ((unsigned int *) &mutex->__data.__lock, 1, private);
/* We must clear op_pending after we release the mutex.
FIXME However, this violates the mutex destruction requirements
because another thread could acquire the mutex, destroy it, and
reuse the memory for something else; then, if this thread crashes,
and the memory happens to have a value equal to the TID, the kernel
will believe it is still related to the mutex (which has been
destroyed already) and will modify some other random object. */
__asm ("" ::: "memory");
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
Then Process 1, Thread B runs, grabs the lock, releases it, and based on
program state it knows it can pthread_mutex_destroy() this lock, free its
associated memory through the custom shared memory allocator, and allocate
it for other purposes. Then we get to the point where Process 1 is
killed, and where the robust futex kernel code corrupts data in shared
memory because of the dangling list_op_pending pointer.
That shared memory data is still observable by Process B, which will get a
corrupted state.
Notice how this all happens without any munmap(2)/mmap(2) in the sequence ?
This is why I think this is purely a userspace issue rather than an issue
we can solve by adding extra synchronization in the kernel.
The one point we have in that sequence where I think we can add synchronization
is pthread_mutex_destroy(3) in libc. One possible "big hammer" solution would be
to make pthread_mutex_destroy iterate on all other threads list_op_pending
and busy-wait if it finds that the mutex address is in use. It would of course
only have to do that for robust futexes.
If that big hammer solution is not fast enough for many-threaded use-cases,
then we can think of other approaches such as adding a reference counter
in the mutex structure, or introducing hazard pointers in userspace to reduce
synchronization iteration from nr_threads to nr_cpus (or even down to max
rseq mm_cid).
Thoughts ?
Thanks,
Mathieu
>
> Thanks!
> André
>
> [0] https://lore.kernel.org/lkml/20251122-tonyk-robust_futex-v6-0-05fea005a0fd@igalia.com/
> [1] https://lpc.events/event/19/contributions/2108/
> [2] https://lore.kernel.org/lkml/20241219171344.GA26279@noisy.programming.kicks-ass.net/
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
^ permalink raw reply
* Re: [RFC PATCH 0/2] futex: how to solve the robust_list race condition?
From: Mathieu Desnoyers @ 2026-02-20 22:41 UTC (permalink / raw)
To: André Almeida, Carlos O'Donell,
Sebastian Andrzej Siewior, Peter Zijlstra, Florian Weimer,
Rich Felker, Torvald Riegel, Darren Hart, Thomas Gleixner,
Ingo Molnar, Davidlohr Bueso, Arnd Bergmann, Liam R . Howlett,
Lorenzo Stoakes, Michal Hocko
Cc: kernel-dev, linux-api, linux-kernel, libc-alpha
In-Reply-To: <0d334517-63ee-46c9-884d-6c2ae8388b87@efficios.com>
On 2026-02-20 16:42, Mathieu Desnoyers wrote:
> +CC libc-alpha.
>
> On 2026-02-20 15:26, André Almeida wrote:
>> During LPC 2025, I presented a session about creating a new syscall for
>> robust_list[0][1]. However, most of the session discussion wasn't much
>> related
>> to the new syscall itself, but much more related to an old bug that
>> exists in
>> the current robust_list mechanism.
>>
>> Since at least 2012, there's an open bug reporting a race condition, as
>> Carlos O'Donell pointed out:
>>
>> "File corruption race condition in robust mutex unlocking"
>> https://sourceware.org/bugzilla/show_bug.cgi?id=14485
>>
>> To help understand the bug, I've created a reproducer (patch 1/2) and a
>> companion kernel hack (patch 2/2) that helps to make the race condition
>> more likely. When the bug happens, the reproducer shows a message
>> comparing the original memory with the corrupted one:
>>
>> "Memory was corrupted by the kernel: 8001fe8d8001fe8d vs
>> 8001fe8dc0000000"
>>
>> I'm not sure yet what would be the appropriated approach to fix it, so I
>> decided to reach the community before moving forward in some direction.
>> One suggestion from Peter[2] resolves around serializing the mmap()
>> and the
>> robust list exit path, which might cause overheads for the common case,
>> where list_op_pending is empty.
>>
>> However, giving that there's a new interface being prepared, this could
>> also give the opportunity to rethink how list_op_pending works, and get
>> rid of the race condition by design.
>>
>> Feedback is very much welcome.
>
> Looking at this bug, one thing I'm starting to consider is that it
> appears to be an issue inherent to lack of synchronization between
> pthread_mutex_destroy(3) and the per-thread list_op_pending fields
> and not so much a kernel issue.
>
> Here is why I think the issue is purely userspace:
>
> Let's suppose we have a shared memory area across Processes 1 and
> Process 2,
> which internally have its own custom memory allocator in userspace to
> allocate/free space within that shared memory.
>
> Process 1, Thread A stumbles through the scenario highlighted by this
> bug, and
> basically gets preempted at this FIXME in libc
> __pthread_mutex_unlock_full():
>
> if (__glibc_unlikely ((atomic_exchange_release (&mutex-
> >__data.__lock, 0)
> & FUTEX_WAITERS) != 0))
> futex_wake ((unsigned int *) &mutex->__data.__lock, 1, private);
>
> /* We must clear op_pending after we release the mutex.
> FIXME However, this violates the mutex destruction requirements
> because another thread could acquire the mutex, destroy it, and
> reuse the memory for something else; then, if this thread
> crashes,
> and the memory happens to have a value equal to the TID, the
> kernel
> will believe it is still related to the mutex (which has been
> destroyed already) and will modify some other random object. */
> __asm ("" ::: "memory");
> THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
>
> Then Process 1, Thread B runs, grabs the lock, releases it, and based on
> program state it knows it can pthread_mutex_destroy() this lock, free its
> associated memory through the custom shared memory allocator, and allocate
> it for other purposes. Then we get to the point where Process 1 is
> killed, and where the robust futex kernel code corrupts data in shared
> memory because of the dangling list_op_pending pointer.
>
> That shared memory data is still observable by Process B, which will get a
> corrupted state.
>
> Notice how this all happens without any munmap(2)/mmap(2) in the sequence ?
> This is why I think this is purely a userspace issue rather than an issue
> we can solve by adding extra synchronization in the kernel.
>
> The one point we have in that sequence where I think we can add
> synchronization
> is pthread_mutex_destroy(3) in libc. One possible "big hammer" solution
> would be
> to make pthread_mutex_destroy iterate on all other threads list_op_pending
> and busy-wait if it finds that the mutex address is in use. It would of
> course
> only have to do that for robust futexes.
>
> If that big hammer solution is not fast enough for many-threaded use-cases,
> then we can think of other approaches such as adding a reference counter
> in the mutex structure, or introducing hazard pointers in userspace to
> reduce
> synchronization iteration from nr_threads to nr_cpus (or even down to max
> rseq mm_cid).
To make matters even worse, the pthread_mutex_destroy(3) and reallocation
could happen from Process 2 rather than Process 1. So iterating on a
threads from Process 1 is not sufficient. We'd need to synchronize
pthread_mutex_destroy on something within the mutex structure which is
observable from all processes using the lock, for instance a reference count.
Thanks,
Mathieu
>
> Thoughts ?
>
> Thanks,
>
> Mathieu
>
>>
>> Thanks!
>> André
>>
>> [0] https://lore.kernel.org/lkml/20251122-tonyk-robust_futex-
>> v6-0-05fea005a0fd@igalia.com/
>> [1] https://lpc.events/event/19/contributions/2108/
>> [2] https://lore.kernel.org/
>> lkml/20241219171344.GA26279@noisy.programming.kicks-ass.net/
>
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
^ permalink raw reply
* Re: [RFC PATCH 0/2] futex: how to solve the robust_list race condition?
From: Mathieu Desnoyers @ 2026-02-20 23:17 UTC (permalink / raw)
To: André Almeida, Carlos O'Donell,
Sebastian Andrzej Siewior, Peter Zijlstra, Florian Weimer,
Rich Felker, Torvald Riegel, Darren Hart, Thomas Gleixner,
Ingo Molnar, Davidlohr Bueso, Arnd Bergmann, Liam R . Howlett,
Lorenzo Stoakes, Michal Hocko
Cc: kernel-dev, linux-api, linux-kernel, libc-alpha
In-Reply-To: <67be0aa1-2241-43ef-aa01-a89ced26c8f6@efficios.com>
On 2026-02-20 17:41, Mathieu Desnoyers wrote:
> On 2026-02-20 16:42, Mathieu Desnoyers wrote:
>> +CC libc-alpha.
>>
>> On 2026-02-20 15:26, André Almeida wrote:
>>> During LPC 2025, I presented a session about creating a new syscall for
>>> robust_list[0][1]. However, most of the session discussion wasn't
>>> much related
>>> to the new syscall itself, but much more related to an old bug that
>>> exists in
>>> the current robust_list mechanism.
>>>
>>> Since at least 2012, there's an open bug reporting a race condition, as
>>> Carlos O'Donell pointed out:
>>>
>>> "File corruption race condition in robust mutex unlocking"
>>> https://sourceware.org/bugzilla/show_bug.cgi?id=14485
>>>
>>> To help understand the bug, I've created a reproducer (patch 1/2) and a
>>> companion kernel hack (patch 2/2) that helps to make the race condition
>>> more likely. When the bug happens, the reproducer shows a message
>>> comparing the original memory with the corrupted one:
>>>
>>> "Memory was corrupted by the kernel: 8001fe8d8001fe8d vs
>>> 8001fe8dc0000000"
>>>
>>> I'm not sure yet what would be the appropriated approach to fix it, so I
>>> decided to reach the community before moving forward in some direction.
>>> One suggestion from Peter[2] resolves around serializing the mmap()
>>> and the
>>> robust list exit path, which might cause overheads for the common case,
>>> where list_op_pending is empty.
>>>
>>> However, giving that there's a new interface being prepared, this could
>>> also give the opportunity to rethink how list_op_pending works, and get
>>> rid of the race condition by design.
>>>
>>> Feedback is very much welcome.
>>
>> Looking at this bug, one thing I'm starting to consider is that it
>> appears to be an issue inherent to lack of synchronization between
>> pthread_mutex_destroy(3) and the per-thread list_op_pending fields
>> and not so much a kernel issue.
>>
>> Here is why I think the issue is purely userspace:
>>
>> Let's suppose we have a shared memory area across Processes 1 and
>> Process 2,
>> which internally have its own custom memory allocator in userspace to
>> allocate/free space within that shared memory.
>>
>> Process 1, Thread A stumbles through the scenario highlighted by this
>> bug, and
>> basically gets preempted at this FIXME in libc
>> __pthread_mutex_unlock_full():
>>
>> if (__glibc_unlikely ((atomic_exchange_release (&mutex-
>> >__data.__lock, 0)
>> & FUTEX_WAITERS) != 0))
>> futex_wake ((unsigned int *) &mutex->__data.__lock, 1, private);
>>
>> /* We must clear op_pending after we release the mutex.
>> FIXME However, this violates the mutex destruction requirements
>> because another thread could acquire the mutex, destroy it, and
>> reuse the memory for something else; then, if this thread
>> crashes,
>> and the memory happens to have a value equal to the TID, the
>> kernel
>> will believe it is still related to the mutex (which has been
>> destroyed already) and will modify some other random
>> object. */
>> __asm ("" ::: "memory");
>> THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
>>
>> Then Process 1, Thread B runs, grabs the lock, releases it, and based on
>> program state it knows it can pthread_mutex_destroy() this lock, free its
>> associated memory through the custom shared memory allocator, and
>> allocate
>> it for other purposes. Then we get to the point where Process 1 is
>> killed, and where the robust futex kernel code corrupts data in shared
>> memory because of the dangling list_op_pending pointer.
>>
>> That shared memory data is still observable by Process B, which will
>> get a
>> corrupted state.
>>
>> Notice how this all happens without any munmap(2)/mmap(2) in the
>> sequence ?
>> This is why I think this is purely a userspace issue rather than an issue
>> we can solve by adding extra synchronization in the kernel.
>>
>> The one point we have in that sequence where I think we can add
>> synchronization
>> is pthread_mutex_destroy(3) in libc. One possible "big hammer"
>> solution would be
>> to make pthread_mutex_destroy iterate on all other threads
>> list_op_pending
>> and busy-wait if it finds that the mutex address is in use. It would
>> of course
>> only have to do that for robust futexes.
>>
>> If that big hammer solution is not fast enough for many-threaded use-
>> cases,
>> then we can think of other approaches such as adding a reference counter
>> in the mutex structure, or introducing hazard pointers in userspace to
>> reduce
>> synchronization iteration from nr_threads to nr_cpus (or even down to max
>> rseq mm_cid).
>
> To make matters even worse, the pthread_mutex_destroy(3) and reallocation
> could happen from Process 2 rather than Process 1. So iterating on a
> threads from Process 1 is not sufficient. We'd need to synchronize
> pthread_mutex_destroy on something within the mutex structure which is
> observable from all processes using the lock, for instance a reference
> count.
Trying to find a backward compatible way to solve this may be tricky.
Here is one possible approach I have in mind: Introduce a new syscall,
e.g. sys_cleanup_robust_list(void *addr)
This system call would be invoked on pthread_mutex_destroy(3) of
robust mutexes, and do the following:
- Calculate the offset of @addr within its mapping,
- Iterate on all processes which map the backing store which contain
the lock address @addr.
- Iterate on each thread sibling within each of those processes,
- If the thread has a robust list, and its list_op_pending points
to the same offset within the backing store mapping, clear the
list_op_pending pointer.
The overhead would be added specifically to pthread_mutex_destroy(3),
and only for robust mutexes.
Thoughts ?
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
^ permalink raw reply
* Re: [RFC PATCH 0/2] futex: how to solve the robust_list race condition?
From: Florian Weimer @ 2026-02-23 11:13 UTC (permalink / raw)
To: Mathieu Desnoyers
Cc: André Almeida, Carlos O'Donell,
Sebastian Andrzej Siewior, Peter Zijlstra, Rich Felker,
Torvald Riegel, Darren Hart, Thomas Gleixner, Ingo Molnar,
Davidlohr Bueso, Arnd Bergmann, Liam R . Howlett, Lorenzo Stoakes,
Michal Hocko, kernel-dev, linux-api, linux-kernel, libc-alpha
In-Reply-To: <a1e24288-6ffc-438d-8a2a-d152134c9555@efficios.com>
* Mathieu Desnoyers:
> Trying to find a backward compatible way to solve this may be tricky.
> Here is one possible approach I have in mind: Introduce a new syscall,
> e.g. sys_cleanup_robust_list(void *addr)
>
> This system call would be invoked on pthread_mutex_destroy(3) of
> robust mutexes, and do the following:
>
> - Calculate the offset of @addr within its mapping,
> - Iterate on all processes which map the backing store which contain
> the lock address @addr.
> - Iterate on each thread sibling within each of those processes,
> - If the thread has a robust list, and its list_op_pending points
> to the same offset within the backing store mapping, clear the
> list_op_pending pointer.
>
> The overhead would be added specifically to pthread_mutex_destroy(3),
> and only for robust mutexes.
Would we have to do this for pthread_mutex_destroy only, or also for
pthread_join? It is defined to exit a thread with mutexes still locked,
and the pthread_join call could mean that the application can determine
by its own logic that the backing store can be deallocated.
Thanks,
Florian
^ permalink raw reply
* Re: [RFC PATCH 0/2] futex: how to solve the robust_list race condition?
From: Mathieu Desnoyers @ 2026-02-23 13:37 UTC (permalink / raw)
To: Florian Weimer
Cc: André Almeida, Carlos O'Donell,
Sebastian Andrzej Siewior, Peter Zijlstra, Rich Felker,
Torvald Riegel, Darren Hart, Thomas Gleixner, Ingo Molnar,
Davidlohr Bueso, Arnd Bergmann, Liam R . Howlett, Lorenzo Stoakes,
Michal Hocko, kernel-dev, linux-api, linux-kernel, libc-alpha
In-Reply-To: <lhusearzp8o.fsf@oldenburg.str.redhat.com>
On 2026-02-23 06:13, Florian Weimer wrote:
> * Mathieu Desnoyers:
>
>> Trying to find a backward compatible way to solve this may be tricky.
>> Here is one possible approach I have in mind: Introduce a new syscall,
>> e.g. sys_cleanup_robust_list(void *addr)
>>
>> This system call would be invoked on pthread_mutex_destroy(3) of
>> robust mutexes, and do the following:
>>
>> - Calculate the offset of @addr within its mapping,
>> - Iterate on all processes which map the backing store which contain
>> the lock address @addr.
>> - Iterate on each thread sibling within each of those processes,
>> - If the thread has a robust list, and its list_op_pending points
>> to the same offset within the backing store mapping, clear the
>> list_op_pending pointer.
>>
>> The overhead would be added specifically to pthread_mutex_destroy(3),
>> and only for robust mutexes.
>
> Would we have to do this for pthread_mutex_destroy only, or also for
> pthread_join? It is defined to exit a thread with mutexes still locked,
> and the pthread_join call could mean that the application can determine
> by its own logic that the backing store can be deallocated.
Let me try to wrap my head around this scenario.
AFAIU, the https://man7.org/linux/man-pages/man3/pthread_join.3.html
NOTES section states the following for pthread_join(3):
After a successful call to pthread_join(), the caller is
guaranteed that the target thread has terminated. The caller may
then choose to do any clean-up that is required after termination
of the thread (e.g., freeing memory or other resources that were
allocated to the target thread).
What is the behavior when a thread exits with a mutex locked ? I would
expect that this mutex stays locked and the pthread_join(3) caller gets
to release that mutex and eventually calls pthread_mutex_destroy(3) if
the application logic allows it.
But it looks like you are implying that the pthread_mutex_destroy(3) is
somehow implicit to pthread_join, and I really don't understand that
part. Am I missing something ?
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
^ permalink raw reply
* Re: [RFC PATCH 0/2] futex: how to solve the robust_list race condition?
From: Rich Felker @ 2026-02-23 13:47 UTC (permalink / raw)
To: Mathieu Desnoyers
Cc: Florian Weimer, André Almeida, Carlos O'Donell,
Sebastian Andrzej Siewior, Peter Zijlstra, Torvald Riegel,
Darren Hart, Thomas Gleixner, Ingo Molnar, Davidlohr Bueso,
Arnd Bergmann, Liam R . Howlett, Lorenzo Stoakes, Michal Hocko,
kernel-dev, linux-api, linux-kernel, libc-alpha
In-Reply-To: <87003e32-eae2-41c8-8b83-2530f084b3c7@efficios.com>
On Mon, Feb 23, 2026 at 08:37:13AM -0500, Mathieu Desnoyers wrote:
> On 2026-02-23 06:13, Florian Weimer wrote:
> > * Mathieu Desnoyers:
> >
> > > Trying to find a backward compatible way to solve this may be tricky.
> > > Here is one possible approach I have in mind: Introduce a new syscall,
> > > e.g. sys_cleanup_robust_list(void *addr)
> > >
> > > This system call would be invoked on pthread_mutex_destroy(3) of
> > > robust mutexes, and do the following:
> > >
> > > - Calculate the offset of @addr within its mapping,
> > > - Iterate on all processes which map the backing store which contain
> > > the lock address @addr.
> > > - Iterate on each thread sibling within each of those processes,
> > > - If the thread has a robust list, and its list_op_pending points
> > > to the same offset within the backing store mapping, clear the
> > > list_op_pending pointer.
> > >
> > > The overhead would be added specifically to pthread_mutex_destroy(3),
> > > and only for robust mutexes.
> >
> > Would we have to do this for pthread_mutex_destroy only, or also for
> > pthread_join? It is defined to exit a thread with mutexes still locked,
> > and the pthread_join call could mean that the application can determine
> > by its own logic that the backing store can be deallocated.
> Let me try to wrap my head around this scenario.
>
> AFAIU, the https://man7.org/linux/man-pages/man3/pthread_join.3.html
> NOTES section states the following for pthread_join(3):
>
> After a successful call to pthread_join(), the caller is
> guaranteed that the target thread has terminated. The caller may
> then choose to do any clean-up that is required after termination
> of the thread (e.g., freeing memory or other resources that were
> allocated to the target thread).
>
> What is the behavior when a thread exits with a mutex locked ? I would
> expect that this mutex stays locked
For a robust mutex, if the owning thread exits, the mutex enters
EOWNERDEAD state.
Otherwise, per POSIX the mutex just remains permanently locked and
undestroyable. glibc does not actually implement this for recursive or
errorchecking mutexes, as the tid might get reused and then the new
thread that got the same tid will now behave as if it were the owner
(e.g. it's allowed to take further recursive locks or observe itself
as the owner via EDEADLK). In musl we implement this by putting all
recursive and errorchecking mutexes on a robust list to reassign an
unmatchable tid to them at pthread_exit time.
> and the pthread_join(3) caller gets
> to release that mutex and eventually calls pthread_mutex_destroy(3) if
> the application logic allows it.
No other thread can release the mutex that was left locked unless it
was robust and it goes via the EOWNERDEAD/recovery process. Nor can
you legally call pthread_mutex_destroy on a mutex that's still owned.
Rich
^ permalink raw reply
* Re: [PATCH 1/2] mount: add OPEN_TREE_NAMESPACE
From: Florian Weimer @ 2026-02-24 11:23 UTC (permalink / raw)
To: Christian Brauner
Cc: linux-fsdevel, Jeff Layton, Alexander Viro, Amir Goldstein,
Josef Bacik, Jan Kara, Aleksa Sarai, linux-api, rudi
In-Reply-To: <20251229-work-empty-namespace-v1-1-bfb24c7b061f@kernel.org>
* Christian Brauner:
> diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
> index 5d3f8c9e3a62..acbc22241c9c 100644
> --- a/include/uapi/linux/mount.h
> +++ b/include/uapi/linux/mount.h
> @@ -61,7 +61,8 @@
> /*
> * open_tree() flags.
> */
> -#define OPEN_TREE_CLONE 1 /* Clone the target tree and attach the clone */
> +#define OPEN_TREE_CLONE (1 << 0) /* Clone the target tree and attach the clone */
This change causes pointless -Werror=undef errors in projects that have
settled on the old definition.
Reported here:
Bug 33921 - Building with Linux-7.0-rc1 errors on OPEN_TREE_CLONE
<https://sourceware.org/bugzilla/show_bug.cgi?id=33921>
Thanks,
Florian
^ permalink raw reply
* Re: [PATCH 1/2] mount: add OPEN_TREE_NAMESPACE
From: Christian Brauner @ 2026-02-24 12:05 UTC (permalink / raw)
To: Florian Weimer
Cc: linux-fsdevel, Jeff Layton, Alexander Viro, Amir Goldstein,
Josef Bacik, Jan Kara, Aleksa Sarai, linux-api, rudi
In-Reply-To: <lhuecmaz8p6.fsf@oldenburg.str.redhat.com>
On Tue, Feb 24, 2026 at 12:23:33PM +0100, Florian Weimer wrote:
> * Christian Brauner:
>
> > diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
> > index 5d3f8c9e3a62..acbc22241c9c 100644
> > --- a/include/uapi/linux/mount.h
> > +++ b/include/uapi/linux/mount.h
> > @@ -61,7 +61,8 @@
> > /*
> > * open_tree() flags.
> > */
> > -#define OPEN_TREE_CLONE 1 /* Clone the target tree and attach the clone */
> > +#define OPEN_TREE_CLONE (1 << 0) /* Clone the target tree and attach the clone */
>
> This change causes pointless -Werror=undef errors in projects that have
> settled on the old definition.
>
> Reported here:
>
> Bug 33921 - Building with Linux-7.0-rc1 errors on OPEN_TREE_CLONE
> <https://sourceware.org/bugzilla/show_bug.cgi?id=33921>
Send a patch to change it back, please.
Otherwise it might take a few days until I get around to it.
^ permalink raw reply
* Re: [PATCH 1/2] mount: add OPEN_TREE_NAMESPACE
From: Florian Weimer @ 2026-02-24 13:30 UTC (permalink / raw)
To: Christian Brauner
Cc: linux-fsdevel, Jeff Layton, Alexander Viro, Amir Goldstein,
Josef Bacik, Jan Kara, Aleksa Sarai, linux-api, rudi
In-Reply-To: <20260224-erbitten-kaufleute-6f14e3072c5d@brauner>
* Christian Brauner:
> On Tue, Feb 24, 2026 at 12:23:33PM +0100, Florian Weimer wrote:
>> * Christian Brauner:
>>
>> > diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
>> > index 5d3f8c9e3a62..acbc22241c9c 100644
>> > --- a/include/uapi/linux/mount.h
>> > +++ b/include/uapi/linux/mount.h
>> > @@ -61,7 +61,8 @@
>> > /*
>> > * open_tree() flags.
>> > */
>> > -#define OPEN_TREE_CLONE 1 /* Clone the target tree and attach the clone */
>> > +#define OPEN_TREE_CLONE (1 << 0) /* Clone the target tree and attach the clone */
>>
>> This change causes pointless -Werror=undef errors in projects that have
>> settled on the old definition.
>>
>> Reported here:
>>
>> Bug 33921 - Building with Linux-7.0-rc1 errors on OPEN_TREE_CLONE
>> <https://sourceware.org/bugzilla/show_bug.cgi?id=33921>
>
> Send a patch to change it back, please.
> Otherwise it might take a few days until I get around to it.
Rudi, could you post a patch?
Thanks,
Florian
^ permalink raw reply
* Re: [PATCH 1/2] mount: add OPEN_TREE_NAMESPACE
From: Christian Brauner @ 2026-02-24 14:33 UTC (permalink / raw)
To: Florian Weimer
Cc: linux-fsdevel, Jeff Layton, Alexander Viro, Amir Goldstein,
Josef Bacik, Jan Kara, Aleksa Sarai, linux-api, rudi
In-Reply-To: <lhuv7fmxo8y.fsf@oldenburg.str.redhat.com>
On Tue, Feb 24, 2026 at 02:30:37PM +0100, Florian Weimer wrote:
> * Christian Brauner:
>
> > On Tue, Feb 24, 2026 at 12:23:33PM +0100, Florian Weimer wrote:
> >> * Christian Brauner:
> >>
> >> > diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
> >> > index 5d3f8c9e3a62..acbc22241c9c 100644
> >> > --- a/include/uapi/linux/mount.h
> >> > +++ b/include/uapi/linux/mount.h
> >> > @@ -61,7 +61,8 @@
> >> > /*
> >> > * open_tree() flags.
> >> > */
> >> > -#define OPEN_TREE_CLONE 1 /* Clone the target tree and attach the clone */
> >> > +#define OPEN_TREE_CLONE (1 << 0) /* Clone the target tree and attach the clone */
> >>
> >> This change causes pointless -Werror=undef errors in projects that have
> >> settled on the old definition.
> >>
> >> Reported here:
> >>
> >> Bug 33921 - Building with Linux-7.0-rc1 errors on OPEN_TREE_CLONE
> >> <https://sourceware.org/bugzilla/show_bug.cgi?id=33921>
> >
> > Send a patch to change it back, please.
> > Otherwise it might take a few days until I get around to it.
>
> Rudi, could you post a patch?
I'm a bit confused though and not super happy that you're basically
asking us to be so constrained that we aren't even allowed to change 1
to 1 - just syntactically different.
^ permalink raw reply
* Re: [PATCH 1/2] mount: add OPEN_TREE_NAMESPACE
From: Jan Kara @ 2026-02-26 11:54 UTC (permalink / raw)
To: Christian Brauner
Cc: Florian Weimer, linux-fsdevel, Jeff Layton, Alexander Viro,
Amir Goldstein, Josef Bacik, Jan Kara, Aleksa Sarai, linux-api,
rudi
In-Reply-To: <20260224-kandidat-wohltat-ae8fb7a57738@brauner>
On Tue 24-02-26 15:33:13, Christian Brauner wrote:
> On Tue, Feb 24, 2026 at 02:30:37PM +0100, Florian Weimer wrote:
> > * Christian Brauner:
> >
> > > On Tue, Feb 24, 2026 at 12:23:33PM +0100, Florian Weimer wrote:
> > >> * Christian Brauner:
> > >>
> > >> > diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
> > >> > index 5d3f8c9e3a62..acbc22241c9c 100644
> > >> > --- a/include/uapi/linux/mount.h
> > >> > +++ b/include/uapi/linux/mount.h
> > >> > @@ -61,7 +61,8 @@
> > >> > /*
> > >> > * open_tree() flags.
> > >> > */
> > >> > -#define OPEN_TREE_CLONE 1 /* Clone the target tree and attach the clone */
> > >> > +#define OPEN_TREE_CLONE (1 << 0) /* Clone the target tree and attach the clone */
> > >>
> > >> This change causes pointless -Werror=undef errors in projects that have
> > >> settled on the old definition.
> > >>
> > >> Reported here:
> > >>
> > >> Bug 33921 - Building with Linux-7.0-rc1 errors on OPEN_TREE_CLONE
> > >> <https://sourceware.org/bugzilla/show_bug.cgi?id=33921>
> > >
> > > Send a patch to change it back, please.
> > > Otherwise it might take a few days until I get around to it.
> >
> > Rudi, could you post a patch?
>
> I'm a bit confused though and not super happy that you're basically
> asking us to be so constrained that we aren't even allowed to change 1
> to 1 - just syntactically different.
Agreed, this looks more like a tooling bug than anything else...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply
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