Patch "bio: return EINTR if copying to user space got interrupted" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

bio: return EINTR if copying to user space got interrupted

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
bio-return-eintr-if-copying-to-user-space-got-interrupted.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Hannes Reinecke <[email protected]>
Date: Fri, 12 Feb 2016 09:39:15 +0100
Subject: bio: return EINTR if copying to user space got interrupted

From: Hannes Reinecke <[email protected]>

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.

---
 fs/bio.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

@@ -1096,9 +1096,12 @@ int bio_uncopy_user(struct bio *bio)
 			ret = __bio_copy_iov(bio, 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);
+		}
 	}
 	kfree(bmd);
 	bio_put(bio);

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/bio-return-eintr-if-copying-to-user-space-got-interrupted.patch