[PATCH 5.15 107/128] f2fs: fix to do sanity check on last xattr entry in __f2fs_setxattr()

Greg Kroah-Hartman
2021-12-27T15:49:00Z

From: Chao Yu <chao@kernel.org>

commit 5598b24efaf4892741c798b425d543e4bed357a1 upstream.

As Wenqing Liu reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=215235

- Overview
page fault in f2fs_setxattr() when mount and operate on corrupted image

- Reproduce
tested on kernel 5.16-rc3, 5.15.X under root

1. unzip tmp7.zip
2. ./single.sh f2fs 7

Sometimes need to run the script several times

- Kernel dump
loop0: detected capacity change from 0 to 131072
F2FS-fs (loop0): Found nat_bits in checkpoint
F2FS-fs (loop0): Mounted with checkpoint version = 7548c2ee
BUG: unable to handle page fault for address: ffffe47bc7123f48
RIP: 0010:kfree+0x66/0x320
Call Trace:
__f2fs_setxattr+0x2aa/0xc00 [f2fs]
f2fs_setxattr+0xfa/0x480 [f2fs]
__f2fs_set_acl+0x19b/0x330 [f2fs]
__vfs_removexattr+0x52/0x70
__vfs_removexattr_locked+0xb1/0x140
vfs_removexattr+0x56/0x100
removexattr+0x57/0x80
path_removexattr+0xa3/0xc0
__x64_sys_removexattr+0x17/0x20
do_syscall_64+0x37/0xb0
entry_SYSCALL_64_after_hwframe+0x44/0xae

The root cause is in __f2fs_setxattr(), we missed to do sanity check on
last xattr entry, result in out-of-bound memory access during updating
inconsistent xattr data of target inode.

After the fix, it can detect such xattr inconsistency as below:

F2FS-fs (loop11): inode (7) has invalid last xattr entry, entry_size: 60676
F2FS-fs (loop11): inode (8) has corrupted xattr
F2FS-fs (loop11): inode (8) has corrupted xattr
F2FS-fs (loop11): inode (8) has invalid last xattr entry, entry_size: 47736

Cc: stable@vger.kernel.org
Reported-by: Wenqing Liu <wenqingliu0120@gmail.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/f2fs/xattr.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -684,8 +684,17 @@ static int __f2fs_setxattr(struct inode
}

last = here;
- while (!IS_XATTR_LAST_ENTRY(last))
+ while (!IS_XATTR_LAST_ENTRY(last)) {
+ if ((void *)(last) + sizeof(__u32) > last_base_addr ||
+ (void *)XATTR_NEXT_ENTRY(last) > last_base_addr) {
+ f2fs_err(F2FS_I_SB(inode), "inode (%lu) has invalid last xattr entry, entry_size: %zu",
+ inode->i_ino, ENTRY_SIZE(last));
+ set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK);
+ error = -EFSCORRUPTED;
+ goto exit;
+ }
last = XATTR_NEXT_ENTRY(last);
+ }

newsize = XATTR_ALIGN(sizeof(struct f2fs_xattr_entry) + len + size);