kernel/linux.git/fs/overlayfs, branch v6.6.132

ovl: Fix uninit-value in ovl_fill_real

2026-03-04T12:20:13+00:00

[ Upstream commit 1992330d90dd766fcf1730fd7bf2d6af65370ac4 ] Syzbot reported a KMSAN uninit-value issue in ovl_fill_real. This iusse's call chain is: __do_sys_getdents64() -> iterate_dir() ... -> ext4_readdir() -> fscrypt_fname_alloc_buffer() // alloc -> fscrypt_fname_disk_to_usr // write without tail '\0' -> dir_emit() -> ovl_fill_real() // read by strcmp() The string is used to store the decrypted directory entry name for an encrypted inode. As shown in the call chain, fscrypt_fname_disk_to_usr() write it without null-terminate. However, ovl_fill_real() uses strcmp() to compare the name against "..", which assumes a null-terminated string and may trigger a KMSAN uninit-value warning when the buffer tail contains uninit data. Reported-by: syzbot+d130f98b2c265fae5297@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=d130f98b2c265fae5297 Fixes: 4edb83bb1041 ("ovl: constant d_ino for non-merge dirs") Signed-off-by: Qing Wang Signed-off-by: Amir Goldstein Link: https://patch.msgid.link/20260128132406.23768-2-amir73il@gmail.com Acked-by: Miklos Szeredi Reviewed-by: Eric Biggers Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

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

2025-07-06T09:00:08+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: don't allow datadir only

2025-04-25T08:45:48+00:00

commit eb3a04a8516ee9b5174379306f94279fc90424c4 upstream. In theory overlayfs could support upper layer directly referring to a data layer, but there's no current use case for this. Originally, when data-only layers were introduced, this wasn't allowed, only introduced by the "datadir+" feature, but without actually handling this case, resulting in an Oops. Fix by disallowing datadir without lowerdir. Reported-by: Giuseppe Scrivano Fixes: 24e16e385f22 ("ovl: add support for appending lowerdirs one by one") Cc: # v6.7 Reviewed-by: Amir Goldstein Reviewed-by: Alexander Larsson Reviewed-by: Christian Brauner Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman

ovl: remove unused forward declaration

2025-04-25T08:45:39+00:00

[ Upstream commit a6eb9a4a69cc360b930dad9dc8513f8fd9b3577f ] The ovl_get_verity_xattr() function was never added, only its declaration. Signed-off-by: Giuseppe Scrivano Fixes: 184996e92e86 ("ovl: Validate verity xattr when resolving lowerdata") Reviewed-by: Amir Goldstein Reviewed-by: Alexander Larsson Reviewed-by: Christian Brauner Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin

ovl: fix UAF in ovl_dentry_update_reval by moving dput() in ovl_link_up

2025-03-07T15:45:36+00:00

[ Upstream commit c84e125fff2615b4d9c259e762596134eddd2f27 ] The issue was caused by dput(upper) being called before ovl_dentry_update_reval(), while upper->d_flags was still accessed in ovl_dentry_remote(). Move dput(upper) after its last use to prevent use-after-free. BUG: KASAN: slab-use-after-free in ovl_dentry_remote fs/overlayfs/util.c:162 [inline] BUG: KASAN: slab-use-after-free in ovl_dentry_update_reval+0xd2/0xf0 fs/overlayfs/util.c:167 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114 print_address_description mm/kasan/report.c:377 [inline] print_report+0xc3/0x620 mm/kasan/report.c:488 kasan_report+0xd9/0x110 mm/kasan/report.c:601 ovl_dentry_remote fs/overlayfs/util.c:162 [inline] ovl_dentry_update_reval+0xd2/0xf0 fs/overlayfs/util.c:167 ovl_link_up fs/overlayfs/copy_up.c:610 [inline] ovl_copy_up_one+0x2105/0x3490 fs/overlayfs/copy_up.c:1170 ovl_copy_up_flags+0x18d/0x200 fs/overlayfs/copy_up.c:1223 ovl_rename+0x39e/0x18c0 fs/overlayfs/dir.c:1136 vfs_rename+0xf84/0x20a0 fs/namei.c:4893 ... Fixes: b07d5cc93e1b ("ovl: update of dentry revalidate flags after copy up") Reported-by: syzbot+316db8a1191938280eb6@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=316db8a1191938280eb6 Signed-off-by: Vasiliy Kovalev Link: https://lore.kernel.org/r/20250214215148.761147-1-kovalev@altlinux.org Reviewed-by: Amir Goldstein Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

fs: relax assertions on failure to encode file handles

2025-01-23T16:21:19+00:00

commit 974e3fe0ac61de85015bbe5a4990cf4127b304b2 upstream. Encoding file handles is usually performed by a filesystem >encode_fh() method that may fail for various reasons. The legacy users of exportfs_encode_fh(), namely, nfsd and name_to_handle_at(2) syscall are ready to cope with the possibility of failure to encode a file handle. There are a few other users of exportfs_encode_{fh,fid}() that currently have a WARN_ON() assertion when ->encode_fh() fails. Relax those assertions because they are wrong. The second linked bug report states commit 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles") in v6.6 as the regressing commit, but this is not accurate. The aforementioned commit only increases the chances of the assertion and allows triggering the assertion with the reproducer using overlayfs, inotify and drop_caches. Triggering this assertion was always possible with other filesystems and other reasons of ->encode_fh() failures and more particularly, it was also possible with the exact same reproducer using overlayfs that is mounted with options index=on,nfs_export=on also on kernels < v6.6. Therefore, I am not listing the aforementioned commit as a Fixes commit. Backport hint: this patch will have a trivial conflict applying to v6.6.y, and other trivial conflicts applying to stable kernels < v6.6. Reported-by: syzbot+ec07f6f5ce62b858579f@syzkaller.appspotmail.com Tested-by: syzbot+ec07f6f5ce62b858579f@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-unionfs/671fd40c.050a0220.4735a.024f.GAE@google.com/ Reported-by: Dmitry Safonov Closes: https://lore.kernel.org/linux-fsdevel/CAGrbwDTLt6drB9eaUagnQVgdPBmhLfqqxAf3F+Juqy_o6oP8uw@mail.gmail.com/ Cc: stable@vger.kernel.org Signed-off-by: Amir Goldstein Link: https://lore.kernel.org/r/20241219115301.465396-1-amir73il@gmail.com Signed-off-by: Christian Brauner Signed-off-by: Amir Goldstein Signed-off-by: Greg Kroah-Hartman

ovl: support encoding fid from inode with no alias

2025-01-23T16:21:19+00:00

commit c45beebfde34aa71afbc48b2c54cdda623515037 upstream. Dmitry Safonov reported that a WARN_ON() assertion can be trigered by userspace when calling inotify_show_fdinfo() for an overlayfs watched inode, whose dentry aliases were discarded with drop_caches. The WARN_ON() assertion in inotify_show_fdinfo() was removed, because it is possible for encoding file handle to fail for other reason, but the impact of failing to encode an overlayfs file handle goes beyond this assertion. As shown in the LTP test case mentioned in the link below, failure to encode an overlayfs file handle from a non-aliased inode also leads to failure to report an fid with FAN_DELETE_SELF fanotify events. As Dmitry notes in his analyzis of the problem, ovl_encode_fh() fails if it cannot find an alias for the inode, but this failure can be fixed. ovl_encode_fh() seldom uses the alias and in the case of non-decodable file handles, as is often the case with fanotify fid info, ovl_encode_fh() never needs to use the alias to encode a file handle. Defer finding an alias until it is actually needed so ovl_encode_fh() will not fail in the common case of FAN_DELETE_SELF fanotify events. Fixes: 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles") Reported-by: Dmitry Safonov Closes: https://lore.kernel.org/linux-fsdevel/CAOQ4uxiie81voLZZi2zXS1BziXZCM24nXqPAxbu8kxXCUWdwOg@mail.gmail.com/ Signed-off-by: Amir Goldstein Link: https://lore.kernel.org/r/20250105162404.357058-3-amir73il@gmail.com Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

ovl: pass realinode to ovl_encode_real_fh() instead of realdentry

2025-01-23T16:21:18+00:00

commit 07aeefae7ff44d80524375253980b1bdee2396b0 upstream. We want to be able to encode an fid from an inode with no alias. Signed-off-by: Amir Goldstein Link: https://lore.kernel.org/r/20250105162404.357058-2-amir73il@gmail.com Signed-off-by: Christian Brauner Stable-dep-of: c45beebfde34 ("ovl: support encoding fid from inode with no alias") Signed-off-by: Sasha Levin [re-applied over v6.6.71 with conflict resolved] Signed-off-by: Amir Goldstein Signed-off-by: Greg Kroah-Hartman

Revert "ovl: do not encode lower fh with upper sb_writers held"

2025-01-21T08:49:10+00:00

This reverts commit 26423e18cd6f709ca4fe7194c29c11658cd0cdd0 which is commit 5b02bfc1e7e3811c5bf7f0fa626a0694d0dbbd77 upstream. It is reported to part of a series that causes problems in the 6.6.y tree, so revert it at this point in time and it can come back later if still needed. Reported-by: Ignat Korchagin Link: https://lore.kernel.org/r/ACD4D6CC-C4D5-4657-A805-03C34559046E@cloudflare.com Cc: Dmitry Safonov Cc: Amir Goldstein Cc: Christian Brauner Cc: Sasha Levin Signed-off-by: Greg Kroah-Hartman

Revert "ovl: pass realinode to ovl_encode_real_fh() instead of realdentry"

2025-01-21T08:49:10+00:00

This reverts commit a3f8a2b13a277d942c810d2ccc654d5bc824a430 which is commit 07aeefae7ff44d80524375253980b1bdee2396b0 upstream. It is reported to part of a series that causes problems in the 6.6.y tree, so revert it at this point in time and it can come back later if still needed. Reported-by: Ignat Korchagin Link: https://lore.kernel.org/r/ACD4D6CC-C4D5-4657-A805-03C34559046E@cloudflare.com Cc: Dmitry Safonov Cc: Amir Goldstein Cc: Christian Brauner Cc: Sasha Levin Signed-off-by: Greg Kroah-Hartman