If nilfs2 reads a disk image with corrupted segment usage metadata, and its segment usage information is marked as an error for the segment at the write location, nilfs_sufile_set_segment_usage() can trigger WARN_ONs during log writing. Segments newly allocated for writing with nilfs_sufile_alloc() will not have this error flag set, but this unexpected situation will occur if the segment indexed by either nilfs->ns_segnum or nilfs->ns_nextnum (active segment) was marked in error. Fix this issue by inserting a sanity check to treat it as a file system corruption. Since error returns are not allowed during the execution phase where nilfs_sufile_set_segment_usage() is used, this inserts the sanity check into nilfs_sufile_mark_dirty() which pre-reads the buffer containing the segment usage record to be updated and sets it up in a dirty state for writing. In addition, nilfs_sufile_set_segment_usage() is also called when canceling log writing and undoing segment usage update, so in order to avoid issuing the same kernel warning in that case, in case of cancellation, avoid checking the error flag in nilfs_sufile_set_segment_usage(). Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Reported-by: syzbot+14e9f834f6ddecece094@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=14e9f834f6ddecece094 Tested-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> --- Andrew, please apply this patch. This resolves one unexpected kernel WARNING issue reported by syzbot. Thanks, Ryusuke Konishi fs/nilfs2/sufile.c | 42 +++++++++++++++++++++++++++++++++++------- 1 file changed, 35 insertions(+), 7 deletions(-) diff --git a/fs/nilfs2/sufile.c b/fs/nilfs2/sufile.c index 2c6078a6b8ec..58ca7c936393 100644 --- a/fs/nilfs2/sufile.c +++ b/fs/nilfs2/sufile.c @@ -501,15 +501,38 @@ int nilfs_sufile_mark_dirty(struct inode *sufile, __u64 segnum) down_write(&NILFS_MDT(sufile)->mi_sem); ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0, &bh); - if (!ret) { - mark_buffer_dirty(bh); - nilfs_mdt_mark_dirty(sufile); - kaddr = kmap_atomic(bh->b_page); - su = nilfs_sufile_block_get_segment_usage(sufile, segnum, bh, kaddr); + if (ret) + goto out_sem; + + kaddr = kmap_atomic(bh->b_page); + su = nilfs_sufile_block_get_segment_usage(sufile, segnum, bh, kaddr); + if (unlikely(nilfs_segment_usage_error(su))) { + struct the_nilfs *nilfs = sufile->i_sb->s_fs_info; + + kunmap_atomic(kaddr); + brelse(bh); + if (nilfs_segment_is_active(nilfs, segnum)) { + nilfs_error(sufile->i_sb, + "active segment %llu is erroneous", + (unsigned long long)segnum); + } else { + /* + * Segments marked erroneous are never allocated by + * nilfs_sufile_alloc(); only active segments, ie, + * the segments indexed by ns_segnum or ns_nextnum, + * can be erroneous here. + */ + WARN_ON_ONCE(1); + } + ret = -EIO; + } else { nilfs_segment_usage_set_dirty(su); kunmap_atomic(kaddr); + mark_buffer_dirty(bh); + nilfs_mdt_mark_dirty(sufile); brelse(bh); } +out_sem: up_write(&NILFS_MDT(sufile)->mi_sem); return ret; } @@ -536,9 +559,14 @@ int nilfs_sufile_set_segment_usage(struct inode *sufile, __u64 segnum, kaddr = kmap_atomic(bh->b_page); su = nilfs_sufile_block_get_segment_usage(sufile, segnum, bh, kaddr); - WARN_ON(nilfs_segment_usage_error(su)); - if (modtime) + if (modtime) { + /* + * Check segusage error and set su_lastmod only when updating + * this entry with a valid timestamp, not for cancellation. + */ + WARN_ON_ONCE(nilfs_segment_usage_error(su)); su->su_lastmod = cpu_to_le64(modtime); + } su->su_nblocks = cpu_to_le32(nblocks); kunmap_atomic(kaddr); -- 2.34.1
