linux-stable.git/fs/overlayfs, branch linux-5.4.y

ovl: Check for NULL d_inode() in ovl_dentry_upper()

2025-07-17T16:24:51+00:00

[ Upstream commit 8a39f1c870e9d6fbac5638f3a42a6a6363829c49 ]

In ovl_path_type() and ovl_is_metacopy_dentry() GCC notices that it is
possible for OVL_E() to return NULL (which implies that d_inode(dentry)
may be NULL). This would result in out of bounds reads via container_of(),
seen with GCC 15's -Warray-bounds -fdiagnostics-details. For example:

In file included from arch/x86/include/generated/asm/rwonce.h:1,
                 from include/linux/compiler.h:339,
                 from include/linux/export.h:5,
                 from include/linux/linkage.h:7,
                 from include/linux/fs.h:5,
                 from fs/overlayfs/util.c:7:
In function 'ovl_upperdentry_dereference',
    inlined from 'ovl_dentry_upper' at ../fs/overlayfs/util.c:305:9,
    inlined from 'ovl_path_type' at ../fs/overlayfs/util.c:216:6:
include/asm-generic/rwonce.h:44:26: error: array subscript 0 is outside array bounds of 'struct inode[7486503276667837]' [-Werror=array-bounds=]
   44 | #define __READ_ONCE(x)  (*(const volatile __unqual_scalar_typeof(x) *)&(x))
      |                         ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/asm-generic/rwonce.h:50:9: note: in expansion of macro '__READ_ONCE'
   50 |         __READ_ONCE(x);                                                 \
      |         ^~~~~~~~~~~
fs/overlayfs/ovl_entry.h:195:16: note: in expansion of macro 'READ_ONCE'
  195 |         return READ_ONCE(oi->__upperdentry);
      |                ^~~~~~~~~
  'ovl_path_type': event 1
  185 |         return inode ? OVL_I(inode)->oe : NULL;
  'ovl_path_type': event 2

Avoid this by allowing ovl_dentry_upper() to return NULL if d_inode() is
NULL, as that means the problematic dereferencing can never be reached.
Note that this fixes the over-eager compiler warning in an effort to
being able to enable -Warray-bounds globally. There is no known
behavioral bug here.

Suggested-by: Amir Goldstein 
Signed-off-by: Kees Cook 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Sasha Levin

ovl: Filter invalid inodes with missing lookup function

2024-12-14T18:44:43+00:00

commit c8b359dddb418c60df1a69beea01d1b3322bfe83 upstream.

Add a check to the ovl_dentry_weird() function to prevent the
processing of directory inodes that lack the lookup function.
This is important because such inodes can cause errors in overlayfs
when passed to the lowerstack.

Reported-by: syzbot+a8c9d476508bd14a90e5@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=a8c9d476508bd14a90e5
Suggested-by: Miklos Szeredi 
Link: https://lore.kernel.org/linux-unionfs/CAJfpegvx-oS9XGuwpJx=Xe28_jzWx5eRo1y900_ZzWY+=gGzUg@mail.gmail.com/
Signed-off-by: Vasiliy Kovalev 
Cc: 
Signed-off-by: Amir Goldstein 
Signed-off-by: Greg Kroah-Hartman

ovl: skip overlayfs superblocks at global sync

2023-12-08T07:44:27+00:00

[ Upstream commit 32b1924b210a70dcacdf65abd687c5ef86a67541 ]

Stacked filesystems like overlayfs has no own writeback, but they have to
forward syncfs() requests to backend for keeping data integrity.

During global sync() each overlayfs instance calls method ->sync_fs() for
backend although it itself is in global list of superblocks too.  As a
result one syscall sync() could write one superblock several times and send
multiple disk barriers.

This patch adds flag SB_I_SKIP_SYNC into sb->sb_iflags to avoid that.

Reported-by: Dmitry Monakhov 
Signed-off-by: Konstantin Khlebnikov 
Reviewed-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi 
Stable-dep-of: b836c4d29f27 ("ima: detect changes to the backing overlay file")
Signed-off-by: Sasha Levin

overlayfs: set ctime when setting mtime and atime

2023-10-25T09:53:23+00:00

[ Upstream commit 03dbab3bba5f009d053635c729d1244f2c8bad38 ]

Nathan reported that he was seeing the new warning in
setattr_copy_mgtime pop when starting podman containers. Overlayfs is
trying to set the atime and mtime via notify_change without also
setting the ctime.

POSIX states that when the atime and mtime are updated via utimes() that
we must also update the ctime to the current time. The situation with
overlayfs copy-up is analogies, so add ATTR_CTIME to the bitmask.
notify_change will fill in the value.

Reported-by: Nathan Chancellor 
Signed-off-by: Jeff Layton 
Tested-by: Nathan Chancellor 
Acked-by: Christian Brauner 
Acked-by: Amir Goldstein 
Message-Id: <20230913-ctime-v1-1-c6bc509cbc27@kernel.org>
Signed-off-by: Christian Brauner 
Signed-off-by: Sasha Levin

new helper: lookup_positive_unlocked()

2023-09-23T08:59:40+00:00

[ Upstream commit 6c2d4798a8d16cf4f3a28c3cd4af4f1dcbbb4d04 ]

Most of the callers of lookup_one_len_unlocked() treat negatives are
ERR_PTR(-ENOENT).  Provide a helper that would do just that.  Note
that a pinned positive dentry remains positive - it's ->d_inode is
stable, etc.; a pinned _negative_ dentry can become positive at any
point as long as you are not holding its parent at least shared.
So using lookup_one_len_unlocked() needs to be careful;
lookup_positive_unlocked() is safer and that's what the callers
end up open-coding anyway.

Signed-off-by: Al Viro 
Stable-dep-of: 0d5a4f8f775f ("fs: Fix error checking for d_hash_and_lookup()")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

ovl: check type and offset of struct vfsmount in ovl_entry

2023-08-30T14:27:09+00:00

[ Upstream commit f723edb8a532cd26e1ff0a2b271d73762d48f762 ]

Porting overlayfs to the new amount api I started experiencing random
crashes that couldn't be explained easily. So after much debugging and
reasoning it became clear that struct ovl_entry requires the point to
struct vfsmount to be the first member and of type struct vfsmount.

During the port I added a new member at the beginning of struct
ovl_entry which broke all over the place in the form of random crashes
and cache corruptions. While there's a comment in ovl_free_fs() to the
effect of "Hack! Reuse ofs->layers as a vfsmount array before freeing
it" there's no such comment on struct ovl_entry which makes this easy to
trip over.

Add a comment and two static asserts for both the offset and the type of
pointer in struct ovl_entry.

Signed-off-by: Christian Brauner 
Signed-off-by: Amir Goldstein 
Signed-off-by: Sasha Levin

treewide: Remove uninitialized_var() usage

2023-06-09T08:29:01+00:00

commit 3f649ab728cda8038259d8f14492fe400fbab911 upstream.

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.

In preparation for removing[2] the[3] macro[4], remove all remaining
needless uses with the following script:

git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \
	xargs perl -pi -e \
		's/\buninitialized_var\(([^\)]+)\)/\1/g;
		 s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;'

drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid
pathological white-space.

No outstanding warnings were found building allmodconfig with GCC 9.3.0
for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64,
alpha, and m68k.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Reviewed-by: Leon Romanovsky  # drivers/infiniband and mlx4/mlx5
Acked-by: Jason Gunthorpe  # IB
Acked-by: Kalle Valo  # wireless drivers
Reviewed-by: Chao Yu  # erofs
Signed-off-by: Kees Cook 
Signed-off-by: Greg Kroah-Hartman

ovl: Use ovl mounter's fsuid and fsgid in ovl_link()

2023-01-18T10:41:43+00:00

commit 5b0db51215e895a361bc63132caa7cca36a53d6a upstream.

There is a wrong case of link() on overlay:
  $ mkdir /lower /fuse /merge
  $ mount -t fuse /fuse
  $ mkdir /fuse/upper /fuse/work
  $ mount -t overlay /merge -o lowerdir=/lower,upperdir=/fuse/upper,\
    workdir=work
  $ touch /merge/file
  $ chown bin.bin /merge/file // the file's caller becomes "bin"
  $ ln /merge/file /merge/lnkfile

Then we will get an error(EACCES) because fuse daemon checks the link()'s
caller is "bin", it denied this request.

In the changing history of ovl_link(), there are two key commits:

The first is commit bb0d2b8ad296 ("ovl: fix sgid on directory") which
overrides the cred's fsuid/fsgid using the new inode. The new inode's
owner is initialized by inode_init_owner(), and inode->fsuid is
assigned to the current user. So the override fsuid becomes the
current user. We know link() is actually modifying the directory, so
the caller must have the MAY_WRITE permission on the directory. The
current caller may should have this permission. This is acceptable
to use the caller's fsuid.

The second is commit 51f7e52dc943 ("ovl: share inode for hard link")
which removed the inode creation in ovl_link(). This commit move
inode_init_owner() into ovl_create_object(), so the ovl_link() just
give the old inode to ovl_create_or_link(). Then the override fsuid
becomes the old inode's fsuid, neither the caller nor the overlay's
mounter! So this is incorrect.

Fix this bug by using ovl mounter's fsuid/fsgid to do underlying
fs's link().

Link: https://lore.kernel.org/all/20220817102952.xnvesg3a7rbv576x@wittgenstein/T
Link: https://lore.kernel.org/lkml/20220825130552.29587-1-zhangtianci.1997@bytedance.com/t
Signed-off-by: Zhang Tianci 
Signed-off-by: Jiachen Zhang 
Reviewed-by: Christian Brauner (Microsoft) 
Fixes: 51f7e52dc943 ("ovl: share inode for hard link")
Cc:  # v4.8
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

ovl: drop WARN_ON() dentry is NULL in ovl_encode_fh()

2022-08-25T09:17:23+00:00

commit dd524b7f317de8d31d638cbfdc7be4cf9b770e42 upstream.

Some code paths cannot guarantee the inode have any dentry alias. So
WARN_ON() all !dentry may flood the kernel logs.

For example, when an overlayfs inode is watched by inotifywait (1), and
someone is trying to read the /proc/$(pidof inotifywait)/fdinfo/INOTIFY_FD,
at that time if the dentry has been reclaimed by kernel (such as
echo 2 > /proc/sys/vm/drop_caches), there will be a WARN_ON(). The
printed call stack would be like:

    ? show_mark_fhandle+0xf0/0xf0
    show_mark_fhandle+0x4a/0xf0
    ? show_mark_fhandle+0xf0/0xf0
    ? seq_vprintf+0x30/0x50
    ? seq_printf+0x53/0x70
    ? show_mark_fhandle+0xf0/0xf0
    inotify_fdinfo+0x70/0x90
    show_fdinfo.isra.4+0x53/0x70
    seq_show+0x130/0x170
    seq_read+0x153/0x440
    vfs_read+0x94/0x150
    ksys_read+0x5f/0xe0
    do_syscall_64+0x59/0x1e0
    entry_SYSCALL_64_after_hwframe+0x44/0xa9

So let's drop WARN_ON() to avoid kernel log flooding.

Reported-by: Hongbo Yin 
Signed-off-by: Jiachen Zhang 
Signed-off-by: Tianci Zhang 
Fixes: 8ed5eec9d6c4 ("ovl: encode pure upper file handles")
Cc:  # v4.16
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

ovl: fix warning in ovl_create_real()

2021-12-22T08:29:40+00:00

commit 1f5573cfe7a7056e80a92c7a037a3e69f3a13d1c upstream.

Syzbot triggered the following warning in ovl_workdir_create() ->
ovl_create_real():

	if (!err && WARN_ON(!newdentry->d_inode)) {

The reason is that the cgroup2 filesystem returns from mkdir without
instantiating the new dentry.

Weird filesystems such as this will be rejected by overlayfs at a later
stage during setup, but to prevent such a warning, call ovl_mkdir_real()
directly from ovl_workdir_create() and reject this case early.

Reported-and-tested-by: syzbot+75eab84fd0af9e8bf66b@syzkaller.appspotmail.com
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman