In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix to do sanity check on i_xattr_nid in sanity_check_inode()

syzbot reports a kernel bug as below:

F2FS-fs (loop0): Mounted with checkpoint version = 48b305e4

BUG: KASAN: slab-out-of-bounds in f2fs_test_bit fs/f2fs/f2fs.h:2933 [inline] BUG: KASAN: slab-out-of-bounds in current_nat_addr fs/f2fs/node.h:213 [inline] BUG: KASAN: slab-out-of-bounds in f2fs_get_node_info+0xece/0x1200 fs/f2fs/node.c:600 Read of size 1 at addr ffff88807a58c76c by task syz-executor280/5076

CPU: 1 PID: 5076 Comm: syz-executor280 Not tainted 6.9.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114 print_address_description mm/kasan/report.c:377 [inline] print_report+0x169/0x550 mm/kasan/report.c:488 kasan_report+0x143/0x180 mm/kasan/report.c:601 f2fs_test_bit fs/f2fs/f2fs.h:2933 [inline] current_nat_addr fs/f2fs/node.h:213 [inline] f2fs_get_node_info+0xece/0x1200 fs/f2fs/node.c:600 f2fs_xattr_fiemap fs/f2fs/data.c:1848 [inline] f2fs_fiemap+0x55d/0x1ee0 fs/f2fs/data.c:1925 ioctl_fiemap fs/ioctl.c:220 [inline] do_vfs_ioctl+0x1c07/0x2e50 fs/ioctl.c:838 __do_sys_ioctl fs/ioctl.c:902 [inline] __se_sys_ioctl+0x81/0x170 fs/ioctl.c:890 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The root cause is we missed to do sanity check on i_xattr_nid during f2fs_iget(), so that in fiemap() path, current_nat_addr() will access nat_bitmap w/ offset from invalid i_xattr_nid, result in triggering kasan bug report, fix it.

Affected Software

References

• https://git.kernel.org/stable/c/1640dcf383cdba52be8b28d2a1a2aa7ef7a30c98
• https://git.kernel.org/stable/c/20faaf30e55522bba2b56d9c46689233205d7717
• https://git.kernel.org/stable/c/68e3cd4ecb8603936cccdc338929130045df2e57
• https://git.kernel.org/stable/c/75c87e2ac6149abf44bdde0dd6d541763ddb0dff
• https://git.kernel.org/stable/c/8c8aa473fe6eb46a4bf99f3ea2dbe52bf0c1a1f0
• https://git.kernel.org/stable/c/be0155202e431f3007778568a72432c68f8946ba
• https://git.kernel.org/stable/c/c559a8d840562fbfce9f318448dda2f7d3e6d8e8