| From | Ben Hutchings <> | Date | Wed, 27 Apr 2016 01:02:24 +0200 | Subject | [PATCH 3.2 099/115] bio: return EINTR if copying to user space got interrupted |
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3.2.80-rc1 review patch. If anyone has any objections, please let me know.
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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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