2017-04-11 10:16:04

by Michael Wang

Subject: [PATCH] md: return 0 instead of error in rdev_attr_show()

sysfs_kf_read() expect the show() callback return the dumped
length, while rdev_attr_show() can return the error which lead
into overflow:

BUG: unable to handle kernel paging request at ffff88040b084000
IP: [<ffffffff812fe8f4>] __memmove+0x24/0x1a0
PGD 1edb067 PUD 1ede067 PMD 406b9a063 PTE 800000040b084161
Oops: 0003 [#1] SMP
[snip]
Call Trace:
[<ffffffff81208c30>] ? sysfs_kf_read+0x80/0xb0
[<ffffffff81207e0b>] kernfs_fop_read+0xab/0x160
[<ffffffff81190be8>] __vfs_read+0x28/0xd0
[<ffffffff811911f6>] vfs_read+0x86/0x130
[<ffffffff81191fa6>] SyS_read+0x46/0xa0
[<ffffffff8158bc97>] entry_SYSCALL_64_fastpath+0x12/0x6a

Simply return 0 in case of error solved the problem.

Signed-off-by: Michael Wang <[email protected]>
---
drivers/md/md.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 1db88d7..d46d714 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3271,10 +3271,9 @@ rdev_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
struct rdev_sysfs_entry *entry = container_of(attr, struct rdev_sysfs_entry, attr);
struct md_rdev *rdev = container_of(kobj, struct md_rdev, kobj);

- if (!entry->show)
- return -EIO;
- if (!rdev->mddev)
- return -EBUSY;
+ if (!entry->show || !rdev->mddev)
+ return 0;
+
return entry->show(rdev, page);
}

--
2.5.0

2017-04-11 10:34:10

by Michael Wang

Subject: Re: [PATCH] md: return 0 instead of error in rdev_attr_show()

We found the upstream fix, sorry for the noise...

Regards,
Michael Wang

On 04/11/2017 12:14 PM, Michael Wang wrote:
>
> sysfs_kf_read() expect the show() callback return the dumped
> length, while rdev_attr_show() can return the error which lead
> into overflow:
>
> BUG: unable to handle kernel paging request at ffff88040b084000
> IP: [<ffffffff812fe8f4>] __memmove+0x24/0x1a0
> PGD 1edb067 PUD 1ede067 PMD 406b9a063 PTE 800000040b084161
> Oops: 0003 [#1] SMP
> [snip]
> Call Trace:
> [<ffffffff81208c30>] ? sysfs_kf_read+0x80/0xb0
> [<ffffffff81207e0b>] kernfs_fop_read+0xab/0x160
> [<ffffffff81190be8>] __vfs_read+0x28/0xd0
> [<ffffffff811911f6>] vfs_read+0x86/0x130
> [<ffffffff81191fa6>] SyS_read+0x46/0xa0
> [<ffffffff8158bc97>] entry_SYSCALL_64_fastpath+0x12/0x6a
>
> Simply return 0 in case of error solved the problem.
>
> Signed-off-by: Michael Wang <[email protected]>
> ---
> drivers/md/md.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 1db88d7..d46d714 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -3271,10 +3271,9 @@ rdev_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
> struct rdev_sysfs_entry *entry = container_of(attr, struct rdev_sysfs_entry, attr);
> struct md_rdev *rdev = container_of(kobj, struct md_rdev, kobj);
>
> - if (!entry->show)
> - return -EIO;
> - if (!rdev->mddev)
> - return -EBUSY;
> + if (!entry->show || !rdev->mddev)
> + return 0;
> +
> return entry->show(rdev, page);
> }
>
>