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@suse.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
[ luis: backported to 3.16: based on Johannes' backport to 3.14 ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/block/bio.c b/block/bio.c
index 6467e6afdcd980758ea00444bb533e76f68becf0..529e4195724e3c709218a51dc04be7c3abbdbea1 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -1110,9 +1110,12 @@ 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);