From: Siddh Raman Pant via Linux-erofs <linux-erofs@lists.ozlabs.org> To: Gao Xiang <hsiangkao@linux.alibaba.com>, Chao Yu <chao@kernel.org>, Yue Hu <huyue2@coolpad.com>, Jeffle Xu <jefflexu@linux.alibaba.com> Cc: linux-erofs <linux-erofs@lists.ozlabs.org>, linux-kernel <linux-kernel@vger.kernel.org>, syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com Subject: [PATCH v2] erofs/zmap.c: Fix incorrect offset calculation Date: Fri, 9 Dec 2022 15:51:51 +0530 [thread overview] Message-ID: <20221209102151.311049-1-code@siddh.me> (raw) 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> --- Changes since v2: - Fix the calculation instead of bailing out. fs/erofs/zmap.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c index 0bb66927e3d0..a171e4caba3c 100644 --- a/fs/erofs/zmap.c +++ b/fs/erofs/zmap.c @@ -790,12 +790,16 @@ 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; -- 2.35.1
WARNING: multiple messages have this Message-ID (diff)
From: Siddh Raman Pant <code@siddh.me> To: Gao Xiang <hsiangkao@linux.alibaba.com>, Chao Yu <chao@kernel.org>, Yue Hu <huyue2@coolpad.com>, Jeffle Xu <jefflexu@linux.alibaba.com> Cc: linux-erofs <linux-erofs@lists.ozlabs.org>, linux-kernel <linux-kernel@vger.kernel.org>, syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com Subject: [PATCH v2] erofs/zmap.c: Fix incorrect offset calculation Date: Fri, 9 Dec 2022 15:51:51 +0530 [thread overview] Message-ID: <20221209102151.311049-1-code@siddh.me> (raw) 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> --- Changes since v2: - Fix the calculation instead of bailing out. fs/erofs/zmap.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c index 0bb66927e3d0..a171e4caba3c 100644 --- a/fs/erofs/zmap.c +++ b/fs/erofs/zmap.c @@ -790,12 +790,16 @@ 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; -- 2.35.1
next reply other threads:[~2022-12-09 10:22 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-12-09 10:21 Siddh Raman Pant via Linux-erofs [this message] 2022-12-09 10:21 ` [PATCH v2] erofs/zmap.c: Fix incorrect offset calculation Siddh Raman Pant 2022-12-10 0:23 ` Gao Xiang 2022-12-10 0:23 ` Gao Xiang 2023-01-09 10:35 ` Chao Yu
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20221209102151.311049-1-code@siddh.me \ --to=linux-erofs@lists.ozlabs.org \ --cc=chao@kernel.org \ --cc=code@siddh.me \ --cc=hsiangkao@linux.alibaba.com \ --cc=huyue2@coolpad.com \ --cc=jefflexu@linux.alibaba.com \ --cc=linux-kernel@vger.kernel.org \ --cc=syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.