As Yanming reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=215894

I have encountered a bug in F2FS file system in kernel v5.17.

I have uploaded the system call sequence as case.c, and a fuzzed image can be found in google net disk

The kernel should enable CONFIG_KASAN=y and CONFIG_KASAN_INLINE=y. You can reproduce the bug by running the following commands:

kernel BUG at fs/f2fs/segment.c:2291! Call Trace: f2fs_invalidate_blocks+0x193/0x2d0 f2fs_fallocate+0x2593/0x4a70 vfs_fallocate+0x2a5/0xac0 ksys_fallocate+0x35/0x70 __x64_sys_fallocate+0x8e/0xf0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae

The root cause is, after image was fuzzed, block mapping info in inode will be inconsistent with SIT table, so in f2fs_fallocate(), it will cause panic when updating SIT with invalid blkaddr.

Let's fix the issue by adding sanity check on block address before updating SIT table with it.

Cc: stable@vger.kernel.org Reported-by: Ming Yan yanming@tju.edu.cn Signed-off-by: Chao Yu chao.yu@oppo.com --- fs/f2fs/file.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index f08e6208e183..342b1f17a033 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -1437,11 +1437,19 @@ static int f2fs_do_zero_range(struct dnode_of_data *dn, pgoff_t start, ret = -ENOSPC; break; } - if (dn->data_blkaddr != NEW_ADDR) { - f2fs_invalidate_blocks(sbi, dn->data_blkaddr); - dn->data_blkaddr = NEW_ADDR; - f2fs_set_data_blkaddr(dn); + + if (dn->data_blkaddr == NEW_ADDR) + continue; + + if (!f2fs_is_valid_blkaddr(sbi, dn->data_blkaddr, + DATA_GENERIC_ENHANCE)) { + ret = -EFSCORRUPTED; + break; } + + f2fs_invalidate_blocks(sbi, dn->data_blkaddr); + dn->data_blkaddr = NEW_ADDR; + f2fs_set_data_blkaddr(dn); }

f2fs_update_extent_cache_range(dn, start, 0, index - start);