From: Theodore Ts'o Date: Sat, 29 Apr 2023 20:14:46 +0000 (-0400) Subject: ext4: remove a BUG_ON in ext4_mb_release_group_pa() X-Git-Tag: baikal/aarch64/sdk5.10~178 X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=da762e2cf5a34e237d0bac536894514d07685397;p=kernel.git ext4: remove a BUG_ON in ext4_mb_release_group_pa() commit 463808f237cf73e98a1a45ff7460c2406a150a0b upstream. If a malicious fuzzer overwrites the ext4 superblock while it is mounted such that the s_first_data_block is set to a very large number, the calculation of the block group can underflow, and trigger a BUG_ON check. Change this to be an ext4_warning so that we don't crash the kernel. Cc: stable@kernel.org Link: https://lore.kernel.org/r/20230430154311.579720-3-tytso@mit.edu Reported-by: syzbot+e2efa3efc15a1c9e95c3@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=69b28112e098b070f639efb356393af3ffec4220 Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 3c3166ba43649..caab9781bee7d 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -3895,7 +3895,11 @@ ext4_mb_release_group_pa(struct ext4_buddy *e4b, trace_ext4_mb_release_group_pa(sb, pa); BUG_ON(pa->pa_deleted == 0); ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, &bit); - BUG_ON(group != e4b->bd_group && pa->pa_len != 0); + if (unlikely(group != e4b->bd_group && pa->pa_len != 0)) { + ext4_warning(sb, "bad group: expected %u, group %u, pa_start %llu", + e4b->bd_group, group, pa->pa_pstart); + return 0; + } mb_free_blocks(pa->pa_inode, e4b, bit, pa->pa_len); atomic_add(pa->pa_len, &EXT4_SB(sb)->s_mb_discarded); trace_ext4_mballoc_discard(sb, NULL, group, bit, pa->pa_len);