2013-04-03 15:30:59

by Arnd Bergmann

Subject: [PATCH] block: avoid using uninitialized value in from queue_var_store

As found by gcc-4.8, the QUEUE_SYSFS_BIT_FNS macro creates functions
that use a value generated by queue_var_store independent of whether
that value was set or not.

block/blk-sysfs.c: In function 'queue_store_nonrot':
block/blk-sysfs.c:244:385: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]

Unlike most other such warnings, this one is not a false positive,
writing any non-number string into the sysfs files indeed has
an undefined result, rather than returning an error.

Signed-off-by: Arnd Bergmann <[email protected]>
Cc: Jens Axboe <[email protected]>
---
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 6206a93..5efc5a6 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -229,6 +229,8 @@ queue_store_##name(struct request_queue *q, const char *page, size_t count) \
unsigned long val; \
ssize_t ret; \
ret = queue_var_store(&val, page, count); \
+ if (ret < 0) \
+ return ret; \
if (neg) \
val = !val; \
\

2013-04-03 19:52:38

by Jens Axboe

Subject: Re: [PATCH] block: avoid using uninitialized value in from queue_var_store

On Wed, Apr 03 2013, Arnd Bergmann wrote:
> As found by gcc-4.8, the QUEUE_SYSFS_BIT_FNS macro creates functions
> that use a value generated by queue_var_store independent of whether
> that value was set or not.
>
> block/blk-sysfs.c: In function 'queue_store_nonrot':
> block/blk-sysfs.c:244:385: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]
>
> Unlike most other such warnings, this one is not a false positive,
> writing any non-number string into the sysfs files indeed has
> an undefined result, rather than returning an error.

Huh indeed, thanks Arnd. Queued up.

--
Jens Axboe