https://github.com/torvalds/linux
Revision eab40cf336065e8d765e006b81ff48c5c114b365 authored by Benjamin Block on 03 October 2017, 10:48:37 UTC, committed by Jens Axboe on 04 October 2017, 14:35:04 UTC
When under memory-pressure it is possible that the mempool which backs the 'struct request_queue' will make use of up to BLKDEV_MIN_RQ count emergency buffers - in case it can't get a regular allocation. These buffers are preallocated and once they are also used, they are re-supplied with old finished requests from the same request_queue (see mempool_free()). The bug is, when re-supplying the emergency pool, the old requests are not again ran through the callback mempool_t->alloc(), and thus also not through the callback bsg_init_rq(). Thus we skip initialization, and while the sense-buffer still should be good, scsi_request->cmd might have become to be an invalid pointer in the meantime. When the request is initialized in bsg.c, and the user's CDB is larger than BLK_MAX_CDB, bsg will replace it with a custom allocated buffer, which is freed when the user's command is finished, thus it dangles afterwards. When next a command is sent by the user that has a smaller/similar CDB as BLK_MAX_CDB, bsg will assume that scsi_request->cmd is backed by scsi_request->__cmd, will not make a custom allocation, and write into undefined memory. Fix this by splitting bsg_init_rq() into two functions: - bsg_init_rq() is changed to only do the allocation of the sense-buffer, which is used to back the bsg job's reply buffer. This pointer should never change during the lifetime of a scsi_request, so it doesn't need re-initialization. - bsg_initialize_rq() is a new function that makes use of 'struct request_queue's initialize_rq_fn callback (which was introduced in v4.12). This is always called before the request is given out via blk_get_request(). This function does the remaining initialization that was previously done in bsg_init_rq(), and will also do it when the request is taken from the emergency-pool of the backing mempool. Fixes: 50b4d485528d ("bsg-lib: fix kernel panic resulting from missing allocation of reply-buffer") Cc: <stable@vger.kernel.org> # 4.11+ Reviewed-by: Hannes Reinecke <hare@suse.com> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Benjamin Block <bblock@linux.vnet.ibm.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 parent 70e62f4
Tip revision: eab40cf336065e8d765e006b81ff48c5c114b365 authored by Benjamin Block on 03 October 2017, 10:48:37 UTC
bsg-lib: fix use-after-free under memory-pressure
bsg-lib: fix use-after-free under memory-pressure
Tip revision: eab40cf
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COPYING | -rw-r--r-- | 18.3 KB |
CREDITS | -rw-r--r-- | 96.1 KB |
Kbuild | -rw-r--r-- | 2.2 KB |
Kconfig | -rw-r--r-- | 252 bytes |
MAINTAINERS | -rw-r--r-- | 420.1 KB |
Makefile | -rw-r--r-- | 58.2 KB |
README | -rw-r--r-- | 722 bytes |
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