From: Gao Xiang <xiang@kernel.org> To: Siddh Raman Pant <code@siddh.me> Cc: Gao Xiang <hsiangkao@linux.alibaba.com>, Chao Yu <chao@kernel.org>, Yue Hu <huyue2@coolpad.com>, Jeffle Xu <jefflexu@linux.alibaba.com>, linux-erofs <linux-erofs@lists.ozlabs.org>, linux-kernel <linux-kernel@vger.kernel.org>, syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com Subject: Re: [PATCH v2] erofs/zmap.c: Fix incorrect offset calculation Date: Sat, 10 Dec 2022 08:23:57 +0800 [thread overview] Message-ID: <Y5PRnfFDJkIOXRCB@debian> (raw) In-Reply-To: <20221209102151.311049-1-code@siddh.me> On Fri, Dec 09, 2022 at 03:51:51PM +0530, Siddh Raman Pant via Linux-erofs wrote: > 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> It looks good to me! Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com> Thanks, Gao Xiang > --- > 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: Gao Xiang <xiang@kernel.org> To: Siddh Raman Pant <code@siddh.me> Cc: syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com, linux-kernel <linux-kernel@vger.kernel.org>, Yue Hu <huyue2@coolpad.com>, Gao Xiang <hsiangkao@linux.alibaba.com>, linux-erofs <linux-erofs@lists.ozlabs.org> Subject: Re: [PATCH v2] erofs/zmap.c: Fix incorrect offset calculation Date: Sat, 10 Dec 2022 08:23:57 +0800 [thread overview] Message-ID: <Y5PRnfFDJkIOXRCB@debian> (raw) In-Reply-To: <20221209102151.311049-1-code@siddh.me> On Fri, Dec 09, 2022 at 03:51:51PM +0530, Siddh Raman Pant via Linux-erofs wrote: > 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> It looks good to me! Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com> Thanks, Gao Xiang > --- > 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 prev parent reply other threads:[~2022-12-10 0:24 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-12-09 10:21 [PATCH v2] erofs/zmap.c: Fix incorrect offset calculation Siddh Raman Pant via Linux-erofs 2022-12-09 10:21 ` Siddh Raman Pant 2022-12-10 0:23 ` Gao Xiang [this message] 2022-12-10 0:23 ` Gao Xiang 2023-01-09 10:35 ` Chao Yu
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