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authorMikulas Patocka <mpatocka@redhat.com>2014-02-20 18:01:01 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-06-07 13:25:39 -0700
commit019c8ec9e3c6a3616f10be9eda359f1927d1f8b1 (patch)
tree61faa44380435b19f223fa25d6d393841fb49a37 /drivers/ata/libata-core.c
parentaece4fa7368debd14ac07ebaf569587ff02cc596 (diff)
downloadlinux-linaro-stable-019c8ec9e3c6a3616f10be9eda359f1927d1f8b1.tar.gz
dm crypt: fix cpu hotplug crash by removing per-cpu structure
commit 610f2de3559c383caf8fbbf91e9968102dff7ca0 upstream. The DM crypt target used per-cpu structures to hold pointers to a ablkcipher_request structure. The code assumed that the work item keeps executing on a single CPU, so it didn't use synchronization when accessing this structure. If a CPU is disabled by writing 0 to /sys/devices/system/cpu/cpu*/online, the work item could be moved to another CPU. This causes dm-crypt crashes, like the following, because the code starts using an incorrect ablkcipher_request: smpboot: CPU 7 is now offline BUG: unable to handle kernel NULL pointer dereference at 0000000000000130 IP: [<ffffffffa1862b3d>] crypt_convert+0x12d/0x3c0 [dm_crypt] ... Call Trace: [<ffffffffa1864415>] ? kcryptd_crypt+0x305/0x470 [dm_crypt] [<ffffffff81062060>] ? finish_task_switch+0x40/0xc0 [<ffffffff81052a28>] ? process_one_work+0x168/0x470 [<ffffffff8105366b>] ? worker_thread+0x10b/0x390 [<ffffffff81053560>] ? manage_workers.isra.26+0x290/0x290 [<ffffffff81058d9f>] ? kthread+0xaf/0xc0 [<ffffffff81058cf0>] ? kthread_create_on_node+0x120/0x120 [<ffffffff813464ac>] ? ret_from_fork+0x7c/0xb0 [<ffffffff81058cf0>] ? kthread_create_on_node+0x120/0x120 Fix this bug by removing the per-cpu definition. The structure ablkcipher_request is accessed via a pointer from convert_context. Consequently, if the work item is rescheduled to a different CPU, the thread still uses the same ablkcipher_request. This change may undermine performance improvements intended by commit c0297721 ("dm crypt: scale to multiple cpus") on select hardware. In practice no performance difference was observed on recent hardware. But regardless, correctness is more important than performance. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/ata/libata-core.c')
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