* [PATCH v2] erofs/zmap.c: Fix incorrect offset calculation
@ 2022-12-09 10:21 ` Siddh Raman Pant
0 siblings, 0 replies; 5+ messages in thread
From: Siddh Raman Pant via Linux-erofs @ 2022-12-09 10:21 UTC (permalink / raw)
To: Gao Xiang, Chao Yu, Yue Hu, Jeffle Xu
Cc: linux-erofs, linux-kernel, syzbot+a8e049cd3abd342936b6
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
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH v2] erofs/zmap.c: Fix incorrect offset calculation
@ 2022-12-09 10:21 ` Siddh Raman Pant
0 siblings, 0 replies; 5+ messages in thread
From: Siddh Raman Pant @ 2022-12-09 10:21 UTC (permalink / raw)
To: Gao Xiang, Chao Yu, Yue Hu, Jeffle Xu
Cc: linux-erofs, linux-kernel, syzbot+a8e049cd3abd342936b6
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
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] erofs/zmap.c: Fix incorrect offset calculation
2022-12-09 10:21 ` Siddh Raman Pant
@ 2022-12-10 0:23 ` Gao Xiang
-1 siblings, 0 replies; 5+ messages in thread
From: Gao Xiang @ 2022-12-10 0:23 UTC (permalink / raw)
To: Siddh Raman Pant
Cc: Gao Xiang, Chao Yu, Yue Hu, Jeffle Xu, linux-erofs, linux-kernel,
syzbot+a8e049cd3abd342936b6
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
>
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] erofs/zmap.c: Fix incorrect offset calculation
@ 2022-12-10 0:23 ` Gao Xiang
0 siblings, 0 replies; 5+ messages in thread
From: Gao Xiang @ 2022-12-10 0:23 UTC (permalink / raw)
To: Siddh Raman Pant
Cc: syzbot+a8e049cd3abd342936b6, linux-kernel, Yue Hu, Gao Xiang,
linux-erofs
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
>
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] erofs/zmap.c: Fix incorrect offset calculation
2022-12-09 10:21 ` Siddh Raman Pant
(?)
(?)
@ 2023-01-09 10:35 ` Chao Yu
-1 siblings, 0 replies; 5+ messages in thread
From: Chao Yu @ 2023-01-09 10:35 UTC (permalink / raw)
To: Siddh Raman Pant, Gao Xiang, Yue Hu, Jeffle Xu
Cc: linux-erofs, linux-kernel, syzbot+a8e049cd3abd342936b6
On 2022/12/9 18:21, Siddh Raman Pant 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>
Reviewed-by: Chao Yu <chao@kernel.org>
Thanks,
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-01-09 10:41 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
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
2022-12-10 0:23 ` Gao Xiang
2023-01-09 10:35 ` Chao Yu
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