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authorTejun Heo <tj@kernel.org>2018-07-26 16:37:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-07-26 19:38:03 -0700
commitb512719f771a82180211c9a315b8a7f628832b3d (patch)
tree0edcf7e7fe77de121d6c4ee24f652944493ea901 /include
parentcd3f77d74ac31b4627cdfa70812338076a1ea475 (diff)
download96b-common-b512719f771a82180211c9a315b8a7f628832b3d.tar.gz
delayacct: fix crash in delayacct_blkio_end() after delayacct init failure
While forking, if delayacct init fails due to memory shortage, it continues expecting all delayacct users to check task->delays pointer against NULL before dereferencing it, which all of them used to do. Commit c96f5471ce7d ("delayacct: Account blkio completion on the correct task"), while updating delayacct_blkio_end() to take the target task instead of always using %current, made the function test NULL on %current->delays and then continue to operated on @p->delays. If %current succeeded init while @p didn't, it leads to the following crash. BUG: unable to handle kernel NULL pointer dereference at 0000000000000004 IP: __delayacct_blkio_end+0xc/0x40 PGD 8000001fd07e1067 P4D 8000001fd07e1067 PUD 1fcffbb067 PMD 0 Oops: 0000 [#1] SMP PTI CPU: 4 PID: 25774 Comm: QIOThread0 Not tainted 4.16.0-9_fbk1_rc2_1180_g6b593215b4d7 #9 RIP: 0010:__delayacct_blkio_end+0xc/0x40 Call Trace: try_to_wake_up+0x2c0/0x600 autoremove_wake_function+0xe/0x30 __wake_up_common+0x74/0x120 wake_up_page_bit+0x9c/0xe0 mpage_end_io+0x27/0x70 blk_update_request+0x78/0x2c0 scsi_end_request+0x2c/0x1e0 scsi_io_completion+0x20b/0x5f0 blk_mq_complete_request+0xa2/0x100 ata_scsi_qc_complete+0x79/0x400 ata_qc_complete_multiple+0x86/0xd0 ahci_handle_port_interrupt+0xc9/0x5c0 ahci_handle_port_intr+0x54/0xb0 ahci_single_level_irq_intr+0x3b/0x60 __handle_irq_event_percpu+0x43/0x190 handle_irq_event_percpu+0x20/0x50 handle_irq_event+0x2a/0x50 handle_edge_irq+0x80/0x1c0 handle_irq+0xaf/0x120 do_IRQ+0x41/0xc0 common_interrupt+0xf/0xf Fix it by updating delayacct_blkio_end() check @p->delays instead. Link: http://lkml.kernel.org/r/20180724175542.GP1934745@devbig577.frc2.facebook.com Fixes: c96f5471ce7d ("delayacct: Account blkio completion on the correct task") Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Dave Jones <dsj@fb.com> Debugged-by: Dave Jones <dsj@fb.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Josh Snyder <joshs@netflix.com> Cc: <stable@vger.kernel.org> [4.15+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/delayacct.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/delayacct.h b/include/linux/delayacct.h
index e6c0448ebcc7..31c865d1842e 100644
--- a/include/linux/delayacct.h
+++ b/include/linux/delayacct.h
@@ -124,7 +124,7 @@ static inline void delayacct_blkio_start(void)
static inline void delayacct_blkio_end(struct task_struct *p)
{
- if (current->delays)
+ if (p->delays)
__delayacct_blkio_end(p);
delayacct_clear_flag(DELAYACCT_PF_BLKIO);
}