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Date: Tue, 01 Mar 2016 23:55:22 +0000 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: <linux-kernel@...r.kernel.org> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, <stable@...r.kernel.org>, Johannes Thumshirn <jthumshirn@...e.de>, Hannes Reinecke <hare@...e.de>, Jens Axboe <axboe@...com> Subject: [PATCH 4.4 295/342] bio: return EINTR if copying to user space got interrupted 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hannes Reinecke <hare@...e.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@...e.de> Signed-off-by: Hannes Reinecke <hare@...e.de> Signed-off-by: Jens Axboe <axboe@...com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- block/bio.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/block/bio.c +++ b/block/bio.c @@ -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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