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| author | Siddh Raman Pant <code@siddh.me> | 2022-12-09 15:51:51 +0530 |
|---|---|---|
| committer | Gao Xiang <hsiangkao@linux.alibaba.com> | 2023-01-10 16:38:53 +0800 |
| commit | 6acd87d50998ef0afafc441613aeaf5a8f5c9eff (patch) | |
| tree | db88a2044f3ca5eaeab09cc31fc14a9d95f7cbb5 /fs | |
| parent | 88603b6dc419445847923fcb7fe5080067a30f98 (diff) | |
| download | linux-6acd87d50998ef0afafc441613aeaf5a8f5c9eff.tar.bz2 | |
erofs/zmap.c: Fix incorrect offset calculation
Effective offset to add to length was being incorrectly calculated,
which resulted in iomap->length being set to 0, triggering a WARN_ON
in iomap_iter_done().
Fix that, and describe it in comments.
This was reported as a crash by syzbot under an issue about a warning
encountered in iomap_iter_done(), but unrelated to erofs.
C reproducer: https://syzkaller.appspot.com/text?tag=ReproC&x=1037a6b2880000
Kernel config: https://syzkaller.appspot.com/text?tag=KernelConfig&x=e2021a61197ebe02
Dashboard link: https://syzkaller.appspot.com/bug?extid=a8e049cd3abd342936b6
Reported-by: syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com
Suggested-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Siddh Raman Pant <code@siddh.me>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20221209102151.311049-1-code@siddh.me
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/erofs/zmap.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c index 0150570c33aa..98fb90b9af71 100644 --- a/fs/erofs/zmap.c +++ b/fs/erofs/zmap.c @@ -793,12 +793,16 @@ static int z_erofs_iomap_begin_report(struct inode *inode, loff_t offset, iomap->type = IOMAP_HOLE; iomap->addr = IOMAP_NULL_ADDR; /* - * No strict rule how to describe extents for post EOF, yet - * we need do like below. Otherwise, iomap itself will get + * No strict rule on how to describe extents for post EOF, yet + * we need to do like below. Otherwise, iomap itself will get * into an endless loop on post EOF. + * + * Calculate the effective offset by subtracting extent start + * (map.m_la) from the requested offset, and add it to length. + * (NB: offset >= map.m_la always) */ if (iomap->offset >= inode->i_size) - iomap->length = length + map.m_la - offset; + iomap->length = length + offset - map.m_la; } iomap->flags = 0; return 0; |