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Subject[PATCH 3.2 099/115] bio: return EINTR if copying to user space got interrupted
3.2.80-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Hannes Reinecke <hare@suse.de>

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@suse.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
[bwh: Backported to 3.2:
- Adjust filename
- Put the assignment in the existing 'else' block]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- 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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