[PATCH AUTOSEL 5.17 28/34] stat: fix inconsistency between struct stat and struct compat_stat

[PATCH AUTOSEL 5.17 28/34] stat: fix inconsistency between struct stat and struct compat_stat

[Sasha Levin]

From: Mikulas Patocka <mpatocka@redhat.com>

[ Upstream commit 932aba1e169090357a77af18850a10c256b50819 ]

struct stat (defined in arch/x86/include/uapi/asm/stat.h) has 32-bit
st_dev and st_rdev; struct compat_stat (defined in
arch/x86/include/asm/compat.h) has 16-bit st_dev and st_rdev followed by
a 16-bit padding.

This patch fixes struct compat_stat to match struct stat.

[ Historical note: the old x86 'struct stat' did have that 16-bit field
  that the compat layer had kept around, but it was changes back in 2003
  by "struct stat - support larger dev_t":

    https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=e95b2065677fe32512a597a79db94b77b90c968d

  and back in those days, the x86_64 port was still new, and separate
  from the i386 code, and had already picked up the old version with a
  16-bit st_dev field ]

Note that we can't change compat_dev_t because it is used by
compat_loop_info.

Also, if the st_dev and st_rdev values are 32-bit, we don't have to use
old_valid_dev to test if the value fits into them.  This fixes
-EOVERFLOW on filesystems that are on NVMe because NVMe uses the major
number 259.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/include/asm/compat.h |  6 ++----
 fs/stat.c                     | 19 ++++++++++---------
 2 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index 7516e4199b3c..20fd0acd7d80 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -28,15 +28,13 @@ typedef u16		compat_ipc_pid_t;
 typedef __kernel_fsid_t	compat_fsid_t;
 
 struct compat_stat {
-	compat_dev_t	st_dev;
-	u16		__pad1;
+	u32		st_dev;
 	compat_ino_t	st_ino;
 	compat_mode_t	st_mode;
 	compat_nlink_t	st_nlink;
 	__compat_uid_t	st_uid;
 	__compat_gid_t	st_gid;
-	compat_dev_t	st_rdev;
-	u16		__pad2;
+	u32		st_rdev;
 	u32		st_size;
 	u32		st_blksize;
 	u32		st_blocks;
diff --git a/fs/stat.c b/fs/stat.c
index 28d2020ba1f4..246d138ec066 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -334,9 +334,6 @@ SYSCALL_DEFINE2(fstat, unsigned int, fd, struct __old_kernel_stat __user *, stat
 #  define choose_32_64(a,b) b
 #endif
 
-#define valid_dev(x)  choose_32_64(old_valid_dev(x),true)
-#define encode_dev(x) choose_32_64(old_encode_dev,new_encode_dev)(x)
-
 #ifndef INIT_STRUCT_STAT_PADDING
 #  define INIT_STRUCT_STAT_PADDING(st) memset(&st, 0, sizeof(st))
 #endif
@@ -345,7 +342,9 @@ static int cp_new_stat(struct kstat *stat, struct stat __user *statbuf)
 {
 	struct stat tmp;
 
-	if (!valid_dev(stat->dev) || !valid_dev(stat->rdev))
+	if (sizeof(tmp.st_dev) < 4 && !old_valid_dev(stat->dev))
+		return -EOVERFLOW;
+	if (sizeof(tmp.st_rdev) < 4 && !old_valid_dev(stat->rdev))
 		return -EOVERFLOW;
 #if BITS_PER_LONG == 32
 	if (stat->size > MAX_NON_LFS)
@@ -353,7 +352,7 @@ static int cp_new_stat(struct kstat *stat, struct stat __user *statbuf)
 #endif
 
 	INIT_STRUCT_STAT_PADDING(tmp);
-	tmp.st_dev = encode_dev(stat->dev);
+	tmp.st_dev = new_encode_dev(stat->dev);
 	tmp.st_ino = stat->ino;
 	if (sizeof(tmp.st_ino) < sizeof(stat->ino) && tmp.st_ino != stat->ino)
 		return -EOVERFLOW;
@@ -363,7 +362,7 @@ static int cp_new_stat(struct kstat *stat, struct stat __user *statbuf)
 		return -EOVERFLOW;
 	SET_UID(tmp.st_uid, from_kuid_munged(current_user_ns(), stat->uid));
 	SET_GID(tmp.st_gid, from_kgid_munged(current_user_ns(), stat->gid));
-	tmp.st_rdev = encode_dev(stat->rdev);
+	tmp.st_rdev = new_encode_dev(stat->rdev);
 	tmp.st_size = stat->size;
 	tmp.st_atime = stat->atime.tv_sec;
 	tmp.st_mtime = stat->mtime.tv_sec;
@@ -644,11 +643,13 @@ static int cp_compat_stat(struct kstat *stat, struct compat_stat __user *ubuf)
 {
 	struct compat_stat tmp;
 
-	if (!old_valid_dev(stat->dev) || !old_valid_dev(stat->rdev))
+	if (sizeof(tmp.st_dev) < 4 && !old_valid_dev(stat->dev))
+		return -EOVERFLOW;
+	if (sizeof(tmp.st_rdev) < 4 && !old_valid_dev(stat->rdev))
 		return -EOVERFLOW;
 
 	memset(&tmp, 0, sizeof(tmp));
-	tmp.st_dev = old_encode_dev(stat->dev);
+	tmp.st_dev = new_encode_dev(stat->dev);
 	tmp.st_ino = stat->ino;
 	if (sizeof(tmp.st_ino) < sizeof(stat->ino) && tmp.st_ino != stat->ino)
 		return -EOVERFLOW;
@@ -658,7 +659,7 @@ static int cp_compat_stat(struct kstat *stat, struct compat_stat __user *ubuf)
 		return -EOVERFLOW;
 	SET_UID(tmp.st_uid, from_kuid_munged(current_user_ns(), stat->uid));
 	SET_GID(tmp.st_gid, from_kgid_munged(current_user_ns(), stat->gid));
-	tmp.st_rdev = old_encode_dev(stat->rdev);
+	tmp.st_rdev = new_encode_dev(stat->rdev);
 	if ((u64) stat->size > MAX_NON_LFS)
 		return -EOVERFLOW;
 	tmp.st_size = stat->size;
-- 
2.35.1

[PATCH AUTOSEL 5.17 29/34] VFS: filename_create(): fix incorrect intent.

[Sasha Levin]

From: NeilBrown <neilb@suse.de>

[ Upstream commit b3d4650d82c71b9c9a8184de9e8bb656012b289e ]

When asked to create a path ending '/', but which is not to be a
directory (LOOKUP_DIRECTORY not set), filename_create() will never try
to create the file.  If it doesn't exist, -ENOENT is reported.

However, it still passes LOOKUP_CREATE|LOOKUP_EXCL to the filesystems
->lookup() function, even though there is no intent to create.  This is
misleading and can cause incorrect behaviour.

If you try

   ln -s foo /path/dir/

where 'dir' is a directory on an NFS filesystem which is not currently
known in the dcache, this will fail with ENOENT.

But as the name is not in the dcache, nfs_lookup gets called with
LOOKUP_CREATE|LOOKUP_EXCL and so it returns NULL without performing any
lookup, with the expectation that a subsequent call to create the target
will be made, and the lookup can be combined with the creation.  In the
case with a trailing '/' and no LOOKUP_DIRECTORY, that call is never
made.  Instead filename_create() sees that the dentry is not (yet)
positive and returns -ENOENT - even though the directory actually
exists.

So only set LOOKUP_CREATE|LOOKUP_EXCL if there really is an intent to
create, and use the absence of these flags to decide if -ENOENT should
be returned.

Note that filename_parentat() is only interested in LOOKUP_REVAL, so we
split that out and store it in 'reval_flag'.  __lookup_hash() then gets
reval_flag combined with whatever create flags were determined to be
needed.

Reviewed-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/namei.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 3f1829b3ab5b..509657fdf4f5 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3673,18 +3673,14 @@ static struct dentry *filename_create(int dfd, struct filename *name,
 {
 	struct dentry *dentry = ERR_PTR(-EEXIST);
 	struct qstr last;
+	bool want_dir = lookup_flags & LOOKUP_DIRECTORY;
+	unsigned int reval_flag = lookup_flags & LOOKUP_REVAL;
+	unsigned int create_flags = LOOKUP_CREATE | LOOKUP_EXCL;
 	int type;
 	int err2;
 	int error;
-	bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
 
-	/*
-	 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
-	 * other flags passed in are ignored!
-	 */
-	lookup_flags &= LOOKUP_REVAL;
-
-	error = filename_parentat(dfd, name, lookup_flags, path, &last, &type);
+	error = filename_parentat(dfd, name, reval_flag, path, &last, &type);
 	if (error)
 		return ERR_PTR(error);
 
@@ -3698,11 +3694,13 @@ static struct dentry *filename_create(int dfd, struct filename *name,
 	/* don't fail immediately if it's r/o, at least try to report other errors */
 	err2 = mnt_want_write(path->mnt);
 	/*
-	 * Do the final lookup.
+	 * Do the final lookup.  Suppress 'create' if there is a trailing
+	 * '/', and a directory wasn't requested.
 	 */
-	lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL;
+	if (last.name[last.len] && !want_dir)
+		create_flags = 0;
 	inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
-	dentry = __lookup_hash(&last, path->dentry, lookup_flags);
+	dentry = __lookup_hash(&last, path->dentry, reval_flag | create_flags);
 	if (IS_ERR(dentry))
 		goto unlock;
 
@@ -3716,7 +3714,7 @@ static struct dentry *filename_create(int dfd, struct filename *name,
 	 * all is fine. Let's be bastards - you had / on the end, you've
 	 * been asking for (non-existent) directory. -ENOENT for you.
 	 */
-	if (unlikely(!is_dir && last.name[last.len])) {
+	if (unlikely(!create_flags)) {
 		error = -ENOENT;
 		goto fail;
 	}
-- 
2.35.1