[PATCH v4 1/7] smb: client: fix uid/gid override in getattr with posix extensions

[PATCH v4 1/7] smb: client: fix uid/gid override in getattr with posix extensions

[Paulo Alcantara]

When mounting with 'multiuser,posix' options, cifs_getattr() overrides
the server-provided uid/gid with the current process's fsuid/fsgid.
This is because the condition only checks for unix extensions
(tcon->unix_ext) but not posix extensions (tcon->posix_extensions).

With SMB3 POSIX extensions, the server provides real uid/gid values
just like with unix extensions, so they should be preserved rather
than replaced with the caller's credentials.

Add a tcon->posix_extensions check to the condition so that uid/gid
from the server are properly reported in stat results.

Reported-by: Arthur Lesuisse <arthur.lesuisse@ulb.be>
Closes: https://lore.kernel.org/r/DB9P190MB2012266F6B8DECBE5D26A1798DB52@DB9P190MB2012.EURP190.PROD.OUTLOOK.COM
Suggested-by: Arthur Lesuisse <arthur.lesuisse@ulb.be>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/smb/client/inode.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/smb/client/inode.c b/fs/smb/client/inode.c
index 12ed8db10e00..49f9993ad567 100644
--- a/fs/smb/client/inode.c
+++ b/fs/smb/client/inode.c
@@ -2992,14 +2992,14 @@ int cifs_getattr(struct mnt_idmap *idmap, const struct path *path,
 		stat->attributes |= STATX_ATTR_ENCRYPTED;
 
 	/*
-	 * If on a multiuser mount without unix extensions or cifsacl being
-	 * enabled, and the admin hasn't overridden them, set the ownership
-	 * to the fsuid/fsgid of the current process.
+	 * If on a multiuser mount without unix extensions, posix extensions
+	 * or cifsacl being enabled, and the admin hasn't overridden them,
+	 * set the ownership to the fsuid/fsgid of the current process.
 	 */
 	sbflags = cifs_sb_flags(cifs_sb);
 	if ((sbflags & CIFS_MOUNT_MULTIUSER) &&
 	    !(sbflags & CIFS_MOUNT_CIFS_ACL) &&
-	    !tcon->unix_ext) {
+	    !tcon->unix_ext && !tcon->posix_extensions) {
 		if (!(sbflags & CIFS_MOUNT_OVERR_UID))
 			stat->uid = current_fsuid();
 		if (!(sbflags & CIFS_MOUNT_OVERR_GID))
-- 
2.55.0

[PATCH v4 2/7] smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid

[Paulo Alcantara]

When the administrator mounts with forceuid or forcegid (uid=/gid=
mount options), they expect all files to appear owned by the specified
user/group.  However, several code paths unconditionally called
sid_to_id() to overwrite cf_uid/cf_gid with server-provided values,
ignoring the administrator's explicit override:

  - smb311_posix_info_to_fattr() (stat via POSIX extensions)
  - cifs_posix_to_fattr() (readdir via POSIX extensions)
  - parse_sec_desc() (CIFS ACL ownership mapping)

This allowed an untrusted server to dictate local file ownership even
when the mount was configured to force specific uid/gid values.

Fix all three call sites to check CIFS_MOUNT_OVERR_UID and
CIFS_MOUNT_OVERR_GID before calling sid_to_id(), following the
same pattern already used by cifs_unix_basic_to_fattr() for unix
extensions.

Closes: https://sashiko.dev/#/patchset/20260906155816.603278-1-pc%40manguebit.org
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/smb/client/cifsacl.c | 29 ++++++++++++++++++-----------
 fs/smb/client/inode.c   |  9 +++++++--
 fs/smb/client/readdir.c |  9 +++++++--
 3 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c
index 213a421bf8e9..def8908dd7e9 100644
--- a/fs/smb/client/cifsacl.c
+++ b/fs/smb/client/cifsacl.c
@@ -1346,6 +1346,7 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 {
 	int rc = 0;
 	struct smb_sid *owner_sid_ptr, *group_sid_ptr;
+	unsigned int sbflags = cifs_sb_flags(cifs_sb);
 	struct smb_acl *dacl_ptr; /* no need for SACL ptr */
 	char *end_of_acl;
 	__u32 dacloffset, osidoffset, gsidoffset;
@@ -1364,17 +1365,21 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 	cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n",
 		 pntsd->revision, pntsd->type, osidoffset, gsidoffset,
 		 le32_to_cpu(pntsd->sacloffset), dacloffset);
-/*	cifs_dump_mem("owner_sid: ", owner_sid_ptr, 64); */
+	fattr->cf_uid = cifs_sb->ctx->linux_uid;
+	fattr->cf_gid = cifs_sb->ctx->linux_gid;
+
 	rc = sid_from_sd(pntsd, acl_len, osidoffset, &owner_sid_ptr);
 	if (rc) {
 		cifs_dbg(FYI, "%s: Error %d parsing Owner SID\n", __func__, rc);
 		return rc;
 	}
-	rc = sid_to_id(cifs_sb, owner_sid_ptr, fattr, SIDOWNER);
-	if (rc) {
-		cifs_dbg(FYI, "%s: Error %d mapping Owner SID to uid\n",
-			 __func__, rc);
-		return rc;
+	if (!(sbflags & CIFS_MOUNT_OVERR_UID)) {
+		rc = sid_to_id(cifs_sb, owner_sid_ptr, fattr, SIDOWNER);
+		if (rc) {
+			cifs_dbg(FYI, "%s: Error %d mapping Owner SID to uid\n",
+				 __func__, rc);
+			return rc;
+		}
 	}
 
 	rc = sid_from_sd(pntsd, acl_len, gsidoffset, &group_sid_ptr);
@@ -1383,11 +1388,13 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb,
 			 __func__, rc);
 		return rc;
 	}
-	rc = sid_to_id(cifs_sb, group_sid_ptr, fattr, SIDGROUP);
-	if (rc) {
-		cifs_dbg(FYI, "%s: Error %d mapping Group SID to gid\n",
-			 __func__, rc);
-		return rc;
+	if (!(sbflags & CIFS_MOUNT_OVERR_GID)) {
+		rc = sid_to_id(cifs_sb, group_sid_ptr, fattr, SIDGROUP);
+		if (rc) {
+			cifs_dbg(FYI, "%s: Error %d mapping Group SID to gid\n",
+				 __func__, rc);
+			return rc;
+		}
 	}
 
 	if (dacloffset) {
diff --git a/fs/smb/client/inode.c b/fs/smb/client/inode.c
index 49f9993ad567..1fe0ef0a95db 100644
--- a/fs/smb/client/inode.c
+++ b/fs/smb/client/inode.c
@@ -851,6 +851,7 @@ static void smb311_posix_info_to_fattr(struct cifs_fattr *fattr,
 	struct smb311_posix_qinfo *info = &data->posix_fi;
 	struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
 	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
+	unsigned int sbflags = cifs_sb_flags(cifs_sb);
 
 	memset(fattr, 0, sizeof(*fattr));
 
@@ -895,8 +896,12 @@ static void smb311_posix_info_to_fattr(struct cifs_fattr *fattr,
 		fattr->cf_symlink_target = data->symlink_target;
 		data->symlink_target = NULL;
 	}
-	sid_to_id(cifs_sb, &data->posix_owner, fattr, SIDOWNER);
-	sid_to_id(cifs_sb, &data->posix_group, fattr, SIDGROUP);
+	fattr->cf_uid = cifs_sb->ctx->linux_uid;
+	fattr->cf_gid = cifs_sb->ctx->linux_gid;
+	if (!(sbflags & CIFS_MOUNT_OVERR_UID))
+		sid_to_id(cifs_sb, &data->posix_owner, fattr, SIDOWNER);
+	if (!(sbflags & CIFS_MOUNT_OVERR_GID))
+		sid_to_id(cifs_sb, &data->posix_group, fattr, SIDGROUP);
 
 	cifs_dbg(FYI, "POSIX query info: mode 0x%x uniqueid 0x%llx nlink %d\n",
 		fattr->cf_mode, fattr->cf_uniqueid, fattr->cf_nlink);
diff --git a/fs/smb/client/readdir.c b/fs/smb/client/readdir.c
index 32a75afca8f5..1ea84f4ada39 100644
--- a/fs/smb/client/readdir.c
+++ b/fs/smb/client/readdir.c
@@ -242,6 +242,7 @@ static void
 cifs_posix_to_fattr(struct cifs_fattr *fattr, struct smb2_posix_info *info,
 		    struct cifs_sb_info *cifs_sb)
 {
+	unsigned int sbflags = cifs_sb_flags(cifs_sb);
 	struct smb2_posix_info_parsed parsed;
 
 	posix_info_parse(info, NULL, &parsed);
@@ -281,8 +282,12 @@ cifs_posix_to_fattr(struct cifs_fattr *fattr, struct smb2_posix_info *info,
 		 le32_to_cpu(info->ReparseTag),
 		 le32_to_cpu(info->Mode));
 
-	sid_to_id(cifs_sb, &parsed.owner, fattr, SIDOWNER);
-	sid_to_id(cifs_sb, &parsed.group, fattr, SIDGROUP);
+	fattr->cf_uid = cifs_sb->ctx->linux_uid;
+	fattr->cf_gid = cifs_sb->ctx->linux_gid;
+	if (!(sbflags & CIFS_MOUNT_OVERR_UID))
+		sid_to_id(cifs_sb, &parsed.owner, fattr, SIDOWNER);
+	if (!(sbflags & CIFS_MOUNT_OVERR_GID))
+		sid_to_id(cifs_sb, &parsed.group, fattr, SIDGROUP);
 }
 
 static void __dir_info_to_fattr(struct cifs_fattr *fattr, const void *info)
-- 
2.55.0

[PATCH v4 3/7] smb: client: fix WSL reparse point uid/gid override

[Paulo Alcantara]

wsl_to_fattr() unconditionally overwrites cf_uid/cf_gid with values
from WSL extended attributes ($LXUID/$LXGID), ignoring the forceuid
and forcegid mount options.

Fix this by initializing cf_uid/cf_gid to the mount defaults and
gating the $LXUID/$LXGID EA parsing on forceuid/forcegid.

Closes: https://sashiko.dev/#/patchset/20260906190803.667489-1-pc%40manguebit.org
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/smb/client/reparse.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 5cc5b0410d48..178da801e775 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -1137,10 +1137,14 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
 			 struct cifs_sb_info *cifs_sb,
 			 u32 tag, struct cifs_fattr *fattr)
 {
+	unsigned int sbflags = cifs_sb_flags(cifs_sb);
 	struct smb2_file_full_ea_info *ea;
 	bool have_xattr_dev = false;
 	u32 next = 0;
 
+	fattr->cf_uid = cifs_sb->ctx->linux_uid;
+	fattr->cf_gid = cifs_sb->ctx->linux_gid;
+
 	switch (tag) {
 	case IO_REPARSE_TAG_LX_SYMLINK:
 		fattr->cf_mode |= S_IFLNK;
@@ -1177,11 +1181,13 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
 		nlen = ea->ea_name_length;
 		v = (void *)((u8 *)ea->ea_data + ea->ea_name_length + 1);
 
-		if (!strncmp(name, SMB2_WSL_XATTR_UID, nlen))
-			fattr->cf_uid = wsl_make_kuid(cifs_sb, v);
-		else if (!strncmp(name, SMB2_WSL_XATTR_GID, nlen))
-			fattr->cf_gid = wsl_make_kgid(cifs_sb, v);
-		else if (!strncmp(name, SMB2_WSL_XATTR_MODE, nlen)) {
+		if (!strncmp(name, SMB2_WSL_XATTR_UID, nlen)) {
+			if (!(sbflags & CIFS_MOUNT_OVERR_UID))
+				fattr->cf_uid = wsl_make_kuid(cifs_sb, v);
+		} else if (!strncmp(name, SMB2_WSL_XATTR_GID, nlen)) {
+			if (!(sbflags & CIFS_MOUNT_OVERR_GID))
+				fattr->cf_gid = wsl_make_kgid(cifs_sb, v);
+		} else if (!strncmp(name, SMB2_WSL_XATTR_MODE, nlen)) {
 			/* File type in reparse point tag and in xattr mode must match. */
 			if (S_DT(fattr->cf_mode) != S_DT(le32_to_cpu(*(__le32 *)v)))
 				return false;
-- 
2.55.0

[PATCH v4 4/7] smb: client: avoid using uninitialized SIDs in cifs_posix_to_fattr()

[Paulo Alcantara]

cifs_posix_to_fattr() ignores the return value of posix_info_parse().
When a malformed POSIX directory entry is encountered (e.g. invalid
SID lengths from an untrusted server), posix_info_parse() returns -1
without populating the 'parsed' struct.  The uninitialized stack
memory in parsed.owner and parsed.group is then passed to
sid_to_id(), which processes the garbage bytes and passes them to
request_key() to construct a SID string, potentially leaking kernel
stack contents to the userspace idmap daemon.

Fix this by checking the return value and skipping the SID-to-id
mapping when parsing fails.  The remaining fattr fields (timestamps,
mode, etc.) are populated directly from the 'info' pointer so they
are unaffected.

Closes: https://sashiko.dev/#/patchset/20260906172005.627163-1-pc%40manguebit.org
Closes: https://sashiko.dev/#/patchset/20260906181540.647469-1-pc%40manguebit.org
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/smb/client/readdir.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/fs/smb/client/readdir.c b/fs/smb/client/readdir.c
index 1ea84f4ada39..9530e5b01564 100644
--- a/fs/smb/client/readdir.c
+++ b/fs/smb/client/readdir.c
@@ -244,8 +244,9 @@ cifs_posix_to_fattr(struct cifs_fattr *fattr, struct smb2_posix_info *info,
 {
 	unsigned int sbflags = cifs_sb_flags(cifs_sb);
 	struct smb2_posix_info_parsed parsed;
+	int rc;
 
-	posix_info_parse(info, NULL, &parsed);
+	rc = posix_info_parse(info, NULL, &parsed);
 
 	memset(fattr, 0, sizeof(*fattr));
 	fattr->cf_uniqueid = le64_to_cpu(info->Inode);
@@ -284,10 +285,15 @@ cifs_posix_to_fattr(struct cifs_fattr *fattr, struct smb2_posix_info *info,
 
 	fattr->cf_uid = cifs_sb->ctx->linux_uid;
 	fattr->cf_gid = cifs_sb->ctx->linux_gid;
-	if (!(sbflags & CIFS_MOUNT_OVERR_UID))
-		sid_to_id(cifs_sb, &parsed.owner, fattr, SIDOWNER);
-	if (!(sbflags & CIFS_MOUNT_OVERR_GID))
-		sid_to_id(cifs_sb, &parsed.group, fattr, SIDGROUP);
+	if (rc < 0) {
+		cifs_dbg(VFS, "%s: failed to parse SIDs: %d\n",
+			 __func__, rc);
+	} else {
+		if (!(sbflags & CIFS_MOUNT_OVERR_UID))
+			sid_to_id(cifs_sb, &parsed.owner, fattr, SIDOWNER);
+		if (!(sbflags & CIFS_MOUNT_OVERR_GID))
+			sid_to_id(cifs_sb, &parsed.group, fattr, SIDGROUP);
+	}
 }
 
 static void __dir_info_to_fattr(struct cifs_fattr *fattr, const void *info)
-- 
2.55.0

[PATCH v4 5/7] smb: client: fix file type corruption in wsl_to_fattr()

[Paulo Alcantara]

Setting the file type in cf_mode without clearing the existing S_IFMT
bits first is wrong as it corrupts the file type when cf_mode already
has type bits set (e.g. S_IFREG | S_IFCHR == S_IFLNK).

Clear S_IFMT before the switch statement.

Closes: https://sashiko.dev/#/patchset/20260906172005.627163-1-pc%40manguebit.org
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/smb/client/reparse.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 178da801e775..8a19dee564b8 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -1145,6 +1145,7 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
 	fattr->cf_uid = cifs_sb->ctx->linux_uid;
 	fattr->cf_gid = cifs_sb->ctx->linux_gid;
 
+	fattr->cf_mode &= ~S_IFMT;
 	switch (tag) {
 	case IO_REPARSE_TAG_LX_SYMLINK:
 		fattr->cf_mode |= S_IFLNK;
-- 
2.55.0

[PATCH v4 6/7] smb: client: fix file type corruption in posix_reparse_to_fattr()

[Paulo Alcantara]

Setting the file type in cf_mode without clearing the existing S_IFMT
bits first is wrong as it corrupts the file type when cf_mode already
has type bits set (e.g. S_IFREG | S_IFCHR == S_IFLNK).

Use a local ftype variable to collect the new file type and apply it
after validation succeeds, clearing S_IFMT and setting the new type in
a single assignment.  This avoids stripping cf_mode on malformed
reparse points where the function returns false early.

Closes: https://sashiko.dev/#/patchset/20260906172005.627163-1-pc%40manguebit.org
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/smb/client/reparse.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 8a19dee564b8..616ca2dbfac4 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -1212,6 +1212,7 @@ static bool posix_reparse_to_fattr(struct cifs_sb_info *cifs_sb,
 				   struct cifs_open_info_data *data)
 {
 	struct reparse_nfs_data_buffer *buf = (struct reparse_nfs_data_buffer *)data->reparse.buf;
+	umode_t ftype;
 
 	if (buf == NULL)
 		return true;
@@ -1227,7 +1228,7 @@ static bool posix_reparse_to_fattr(struct cifs_sb_info *cifs_sb,
 			WARN_ON_ONCE(1);
 			return false;
 		}
-		fattr->cf_mode |= S_IFCHR;
+		ftype = S_IFCHR;
 		fattr->cf_rdev = reparse_mkdev(buf->DataBuffer);
 		break;
 	case NFS_SPECFILE_BLK:
@@ -1235,22 +1236,23 @@ static bool posix_reparse_to_fattr(struct cifs_sb_info *cifs_sb,
 			WARN_ON_ONCE(1);
 			return false;
 		}
-		fattr->cf_mode |= S_IFBLK;
+		ftype = S_IFBLK;
 		fattr->cf_rdev = reparse_mkdev(buf->DataBuffer);
 		break;
 	case NFS_SPECFILE_FIFO:
-		fattr->cf_mode |= S_IFIFO;
+		ftype = S_IFIFO;
 		break;
 	case NFS_SPECFILE_SOCK:
-		fattr->cf_mode |= S_IFSOCK;
+		ftype = S_IFSOCK;
 		break;
 	case NFS_SPECFILE_LNK:
-		fattr->cf_mode |= S_IFLNK;
+		ftype = S_IFLNK;
 		break;
 	default:
 		WARN_ON_ONCE(1);
 		return false;
 	}
+	fattr->cf_mode = (fattr->cf_mode & ~S_IFMT) | ftype;
 	return true;
 }
 
-- 
2.55.0

[PATCH v4 7/7] smb: client: fix file type corruption in cifs_reparse_point_to_fattr()

[Paulo Alcantara]

Setting the file type in cf_mode without clearing the existing S_IFMT
bits first is wrong as it corrupts the file type when cf_mode already
has type bits set (e.g. S_IFREG | S_IFLNK == S_IFDIR | S_IFREG).

Clear S_IFMT before setting S_IFLNK for native and SMB1 symlinks.

Closes: https://sashiko.dev/#/patchset/20260906181540.647469-1-pc%40manguebit.org
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/smb/client/reparse.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 616ca2dbfac4..b6bded042e78 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -1280,6 +1280,7 @@ bool cifs_reparse_point_to_fattr(struct cifs_sb_info *cifs_sb,
 		break;
 	case 0: /* SMB1 symlink */
 	case IO_REPARSE_TAG_SYMLINK:
+		fattr->cf_mode &= ~S_IFMT;
 		fattr->cf_mode |= S_IFLNK;
 		break;
 	default:
-- 
2.55.0

Re: [PATCH v4 1/7] smb: client: fix uid/gid override in getattr with posix extensions

[Namjae Jeon]

On Mon, Sep 7, 2026 at 5:05 AM Paulo Alcantara <pc@manguebit.org> wrote:
>
> When mounting with 'multiuser,posix' options, cifs_getattr() overrides
> the server-provided uid/gid with the current process's fsuid/fsgid.
> This is because the condition only checks for unix extensions
> (tcon->unix_ext) but not posix extensions (tcon->posix_extensions).
>
> With SMB3 POSIX extensions, the server provides real uid/gid values
> just like with unix extensions, so they should be preserved rather
> than replaced with the caller's credentials.
>
> Add a tcon->posix_extensions check to the condition so that uid/gid
> from the server are properly reported in stat results.
>
> Reported-by: Arthur Lesuisse <arthur.lesuisse@ulb.be>
> Closes: https://lore.kernel.org/r/DB9P190MB2012266F6B8DECBE5D26A1798DB52@DB9P190MB2012.EURP190.PROD.OUTLOOK.COM
> Suggested-by: Arthur Lesuisse <arthur.lesuisse@ulb.be>
> Signed-off-by: Paulo Alcantara <pc@manguebit.org>
> Cc: Namjae Jeon <linkinjeon@kernel.org>
> Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> Cc: Shyam Prasad N <sprasad@microsoft.com>
> Cc: Tom Talpey <tom@talpey.com>
> Cc: Bharath SM <bharathsm@microsoft.com>
> Cc: stable@vger.kernel.org
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Thanks!

Re: [PATCH v4 2/7] smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid

[Namjae Jeon]

On Mon, Sep 7, 2026 at 5:05 AM Paulo Alcantara <pc@manguebit.org> wrote:
>
> When the administrator mounts with forceuid or forcegid (uid=/gid=
> mount options), they expect all files to appear owned by the specified
> user/group.  However, several code paths unconditionally called
> sid_to_id() to overwrite cf_uid/cf_gid with server-provided values,
> ignoring the administrator's explicit override:
>
>   - smb311_posix_info_to_fattr() (stat via POSIX extensions)
>   - cifs_posix_to_fattr() (readdir via POSIX extensions)
>   - parse_sec_desc() (CIFS ACL ownership mapping)
>
> This allowed an untrusted server to dictate local file ownership even
> when the mount was configured to force specific uid/gid values.
>
> Fix all three call sites to check CIFS_MOUNT_OVERR_UID and
> CIFS_MOUNT_OVERR_GID before calling sid_to_id(), following the
> same pattern already used by cifs_unix_basic_to_fattr() for unix
> extensions.
>
> Closes: https://sashiko.dev/#/patchset/20260906155816.603278-1-pc%40manguebit.org
> Signed-off-by: Paulo Alcantara <pc@manguebit.org>
> Cc: Namjae Jeon <linkinjeon@kernel.org>
> Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> Cc: Shyam Prasad N <sprasad@microsoft.com>
> Cc: Tom Talpey <tom@talpey.com>
> Cc: Bharath SM <bharathsm@microsoft.com>
> Cc: stable@vger.kernel.org
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Thanks!

Re: [PATCH v4 3/7] smb: client: fix WSL reparse point uid/gid override

[Namjae Jeon]

On Mon, Sep 7, 2026 at 5:05 AM Paulo Alcantara <pc@manguebit.org> wrote:
>
> wsl_to_fattr() unconditionally overwrites cf_uid/cf_gid with values
> from WSL extended attributes ($LXUID/$LXGID), ignoring the forceuid
> and forcegid mount options.
>
> Fix this by initializing cf_uid/cf_gid to the mount defaults and
> gating the $LXUID/$LXGID EA parsing on forceuid/forcegid.
>
> Closes: https://sashiko.dev/#/patchset/20260906190803.667489-1-pc%40manguebit.org
> Signed-off-by: Paulo Alcantara <pc@manguebit.org>
> Cc: Namjae Jeon <linkinjeon@kernel.org>
> Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> Cc: Shyam Prasad N <sprasad@microsoft.com>
> Cc: Tom Talpey <tom@talpey.com>
> Cc: Bharath SM <bharathsm@microsoft.com>
> Cc: stable@vger.kernel.org
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Thanks!

Re: [PATCH v4 4/7] smb: client: avoid using uninitialized SIDs in cifs_posix_to_fattr()

[Namjae Jeon]

On Mon, Sep 7, 2026 at 5:05 AM Paulo Alcantara <pc@manguebit.org> wrote:
>
> cifs_posix_to_fattr() ignores the return value of posix_info_parse().
> When a malformed POSIX directory entry is encountered (e.g. invalid
> SID lengths from an untrusted server), posix_info_parse() returns -1
> without populating the 'parsed' struct.  The uninitialized stack
> memory in parsed.owner and parsed.group is then passed to
> sid_to_id(), which processes the garbage bytes and passes them to
> request_key() to construct a SID string, potentially leaking kernel
> stack contents to the userspace idmap daemon.
>
> Fix this by checking the return value and skipping the SID-to-id
> mapping when parsing fails.  The remaining fattr fields (timestamps,
> mode, etc.) are populated directly from the 'info' pointer so they
> are unaffected.
>
> Closes: https://sashiko.dev/#/patchset/20260906172005.627163-1-pc%40manguebit.org
> Closes: https://sashiko.dev/#/patchset/20260906181540.647469-1-pc%40manguebit.org
> Signed-off-by: Paulo Alcantara <pc@manguebit.org>
> Cc: Namjae Jeon <linkinjeon@kernel.org>
> Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> Cc: Shyam Prasad N <sprasad@microsoft.com>
> Cc: Tom Talpey <tom@talpey.com>
> Cc: Bharath SM <bharathsm@microsoft.com>
> Cc: stable@vger.kernel.org
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Thanks!

Re: [PATCH v4 5/7] smb: client: fix file type corruption in wsl_to_fattr()

[Namjae Jeon]

On Mon, Sep 7, 2026 at 5:05 AM Paulo Alcantara <pc@manguebit.org> wrote:
>
> Setting the file type in cf_mode without clearing the existing S_IFMT
> bits first is wrong as it corrupts the file type when cf_mode already
> has type bits set (e.g. S_IFREG | S_IFCHR == S_IFLNK).
>
> Clear S_IFMT before the switch statement.
>
> Closes: https://sashiko.dev/#/patchset/20260906172005.627163-1-pc%40manguebit.org
> Signed-off-by: Paulo Alcantara <pc@manguebit.org>
> Cc: Namjae Jeon <linkinjeon@kernel.org>
> Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> Cc: Shyam Prasad N <sprasad@microsoft.com>
> Cc: Tom Talpey <tom@talpey.com>
> Cc: Bharath SM <bharathsm@microsoft.com>
> Cc: stable@vger.kernel.org
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Thanks!

Re: [PATCH v4 6/7] smb: client: fix file type corruption in posix_reparse_to_fattr()

[Namjae Jeon]

On Mon, Sep 7, 2026 at 5:05 AM Paulo Alcantara <pc@manguebit.org> wrote:
>
> Setting the file type in cf_mode without clearing the existing S_IFMT
> bits first is wrong as it corrupts the file type when cf_mode already
> has type bits set (e.g. S_IFREG | S_IFCHR == S_IFLNK).
>
> Use a local ftype variable to collect the new file type and apply it
> after validation succeeds, clearing S_IFMT and setting the new type in
> a single assignment.  This avoids stripping cf_mode on malformed
> reparse points where the function returns false early.
>
> Closes: https://sashiko.dev/#/patchset/20260906172005.627163-1-pc%40manguebit.org
> Signed-off-by: Paulo Alcantara <pc@manguebit.org>
> Cc: Namjae Jeon <linkinjeon@kernel.org>
> Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> Cc: Shyam Prasad N <sprasad@microsoft.com>
> Cc: Tom Talpey <tom@talpey.com>
> Cc: Bharath SM <bharathsm@microsoft.com>
> Cc: stable@vger.kernel.org
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Thanks!

Re: [PATCH v4 7/7] smb: client: fix file type corruption in cifs_reparse_point_to_fattr()

[Namjae Jeon]

On Mon, Sep 7, 2026 at 5:05 AM Paulo Alcantara <pc@manguebit.org> wrote:
>
> Setting the file type in cf_mode without clearing the existing S_IFMT
> bits first is wrong as it corrupts the file type when cf_mode already
> has type bits set (e.g. S_IFREG | S_IFLNK == S_IFDIR | S_IFREG).
>
> Clear S_IFMT before setting S_IFLNK for native and SMB1 symlinks.
>
> Closes: https://sashiko.dev/#/patchset/20260906181540.647469-1-pc%40manguebit.org
> Signed-off-by: Paulo Alcantara <pc@manguebit.org>
> Cc: Namjae Jeon <linkinjeon@kernel.org>
> Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> Cc: Shyam Prasad N <sprasad@microsoft.com>
> Cc: Tom Talpey <tom@talpey.com>
> Cc: Bharath SM <bharathsm@microsoft.com>
> Cc: stable@vger.kernel.org
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Thanks!