On Sat, 2016-03-19 at 17:00 +0000, Ben Hutchings wrote:
> Commit 2d99b55d378c was marked for inclusion in stable branches from
> 3.11 onwards, as it fixed a bug introduced by a commit in 3.11.
> However, the earlier commit (35dc248383bb "[SCSI] sg: Fix user memory
> corruption when SG_IO is interrupted by a signal") was also
> backported
> to older stable branches, so I believe that 2d99b55d378c is needed in
> those as well.
Here's my (untested) backport to 3.2; looks like it will apply to 3.4.y
and 3.10.y as well.
Ben.
--
Ben Hutchings
The generation of random numbers is too important to be left to chance.
- Robert Coveyou
From: Hannes Reinecke <hare@xxxxxxx>
Date: Fri, 12 Feb 2016 09:39:15 +0100
Subject: bio: return EINTR if copying to user space got interrupted
commit 2d99b55d378c996b9692a0c93dd25f4ed5d58934 upstream.
Commit 35dc248383bbab0a7203fca4d722875bc81ef091 introduced a check for
current->mm to see if we have a user space context and only copies data
if we do. Now if an IO gets interrupted by a signal data isn't copied
into user space any more (as we don't have a user space context) but
user space isn't notified about it.
This patch modifies the behaviour to return -EINTR from bio_uncopy_user()
to notify userland that a signal has interrupted the syscall, otherwise
it could lead to a situation where the caller may get a buffer with
no data returned.
This can be reproduced by issuing SG_IO ioctl()s in one thread while
constantly sending signals to it.
Fixes: 35dc248 [SCSI] sg: Fix user memory corruption when SG_IO is interrupted by a signal
Signed-off-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxx>
[bwh: Backported to 3.2:
- Adjust filename
- Put the assignment in the existing 'else' block]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -793,15 +793,19 @@ int bio_uncopy_user(struct bio *bio)
if (!bio_flagged(bio, BIO_NULL_MAPPED)) {
/*
* if we're in a workqueue, the request is orphaned, so
- * don't copy into a random user address space, just free.
+ * don't copy into a random user address space, just free
+ * and return -EINTR so user space doesn't expect any data.
*/
if (current->mm)
ret = __bio_copy_iov(bio, bmd->iovecs, bmd->sgvecs,
bmd->nr_sgvecs, bio_data_dir(bio) == READ,
0, bmd->is_our_pages);
- else if (bmd->is_our_pages)
- bio_for_each_segment_all(bvec, bio, i)
- __free_page(bvec->bv_page);
+ else {
+ ret = -EINTR;
+ if (bmd->is_our_pages)
+ bio_for_each_segment_all(bvec, bio, i)
+ __free_page(bvec->bv_page);
+ }
}
bio_free_map_data(bmd);
bio_put(bio);
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