From a5b14af4a96cb3103add72ae48907f587e573088 Mon Sep 17 00:00:00 2001 From: Logan Gunthorpe Date: Tue, 10 Dec 2019 11:47:04 -0700 Subject: [PATCH] block: fix NULL pointer dereference in account statistics with IDE The IDE driver creates some passthru requests which never get submitted to the block layer in such a way that blk_account_io_start() gets called. However, the driver still calls __blk_mq_end_request() in ide_end_rq() which will call blk_account_io_completion() which tries to dereferences req->part which is never set. See ide_prep_sense() for an example of where these requests come from. To fix this, blk_account_io_completion() and blk_account_io_done() should do nothing if req->part is not set. The back trace of this bug is: BUG: kernel NULL pointer dereference, address: 000002ac #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page *pde = 00000000 Oops: 0002 [#1] CPU: 0 PID: 237 Comm: kworker/0:1H Not tainted 5.4.0-rc2-00011-g48d9b0d43105e #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 Workqueue: kblockd drive_rq_insert_work EIP: blk_account_io_completion+0x7a/0xf0 Code: 89 54 24 08 31 d2 89 4c 24 04 31 c9 c7 04 24 02 00 00 00 c1 ee 09 e8 f5 21 a6 ff e8 70 5c a7 ff 8b 53 60 8d 04 bd 00 00 00 00 <01> b4 02 ac 02 00 00 8b 9a 88 02 00 00 85 db 74 11 85 d2 74 51 8b EAX: 00000000 EBX: f5b80000 ECX: 00000000 EDX: 00000000 ESI: 00000000 EDI: 00000000 EBP: f3031e70 ESP: f3031e54 DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00010046 CR0: 80050033 CR2: 000002ac CR3: 03c25000 CR4: 000406d0 Call Trace: blk_update_request+0x85/0x420 ide_end_rq+0x38/0xa0 ide_complete_rq+0x3d/0x70 cdrom_newpc_intr+0x258/0xba0 ide_intr+0x135/0x250 __handle_irq_event_percpu+0x3e/0x250 handle_irq_event_percpu+0x1f/0x50 handle_irq_event+0x32/0x60 handle_level_irq+0x6c/0x110 handle_irq+0x72/0xa0 do_IRQ+0x45/0xad common_interrupt+0x115/0x11c Fixes: 9c351d8109d6 ("block: account statistics for passthrough requests") Reported-by: kernel test robot Signed-off-by: Logan Gunthorpe Signed-off-by: Jens Axboe --- block/blk-core.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index a1e228752083f..68c309ce67352 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1310,7 +1310,7 @@ EXPORT_SYMBOL_GPL(blk_rq_err_bytes); void blk_account_io_completion(struct request *req, unsigned int bytes) { - if (blk_do_io_stat(req)) { + if (req->part && blk_do_io_stat(req)) { const int sgrp = op_stat_group(req_op(req)); struct hd_struct *part; @@ -1328,7 +1328,8 @@ void blk_account_io_done(struct request *req, u64 now) * normal IO on queueing nor completion. Accounting the * containing request is enough. */ - if (blk_do_io_stat(req) && !(req->rq_flags & RQF_FLUSH_SEQ)) { + if (req->part && blk_do_io_stat(req) && + !(req->rq_flags & RQF_FLUSH_SEQ)) { const int sgrp = op_stat_group(req_op(req)); struct hd_struct *part; -- 2.39.5