Commit 2d99b55d authored Feb 12, 2016 by Hannes Reinecke Committed by Jens Axboe Feb 12, 2016

bio: return EINTR if copying to user space got interrupted



Commit 35dc2483 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: 35dc2483 [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>
Cc: stable@vger.kernel.org # v.3.11+
Signed-off-by: Jens Axboe <axboe@fb.com>

parent f8e68a7c

block/bio.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -1090,9 +1090,12 @@ 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 && bio_data_dir(bio) == READ)
		if (!current->mm)
		ret = -EINTR;
		else if (bio_data_dir(bio) == READ)
		ret = bio_copy_to_iter(bio, bmd->iter);
		if (bmd->is_our_pages)
		bio_free_pages(bio);

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