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| author | Siddh Raman Pant <code@siddh.me> | 2022-12-09 15:51:51 +0530 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-02-06 08:06:31 +0100 |
| commit | 9f31d8c889d9a4e47bfcc6c4537d0c9f89fe582c (patch) | |
| tree | 67e5978914d554555e8105996997d727918d9e11 /fs | |
| parent | 1283a01b6e19d05f7ed49584ea653947245cd41e (diff) | |
| download | linux-stable-9f31d8c889d9a4e47bfcc6c4537d0c9f89fe582c.tar.gz linux-stable-9f31d8c889d9a4e47bfcc6c4537d0c9f89fe582c.tar.bz2 linux-stable-9f31d8c889d9a4e47bfcc6c4537d0c9f89fe582c.zip | |
erofs/zmap.c: Fix incorrect offset calculation
[ Upstream commit 6acd87d50998ef0afafc441613aeaf5a8f5c9eff ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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 e6d5d7a18fb0..39cc014dba40 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; |