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Chris Wilson authored
A fault in a user provided buffer may lead anywhere, and lockdep warns that we have a potential deadlock between the mm->mmap_sem and the kernfs file mutex: [ 82.811702] ====================================================== [ 82.811705] [ INFO: possible circular locking dependency detected ] [ 82.811709] 4.5.0-rc4-gfxbench+ #1 Not tainted [ 82.811711] ------------------------------------------------------- [ 82.811714] kms_setmode/5859 is trying to acquire lock: [ 82.811717] (&dev->struct_mutex){+.+.+.}, at: [<ffffffff8150d9c1>] drm_gem_mmap+0x1a1/0x270 [ 82.811731] but task is already holding lock: [ 82.811734] (&mm->mmap_sem){++++++}, at: [<ffffffff8117b364>] vm_mmap_pgoff+0x44/0xa0 [ 82.811745] which lock already depends on the new lock. [ 82.811749] the existing dependency chain (in reverse order) is: [ 82.811752] -> #3 (&mm->mmap_sem){++++++}: [ 82.811761] [<ffffffff810cc883>] lock_acquire+0xc3/0x1d0 [ 82.811766] [<ffffffff8118bc65>] __might_fault+0x75/0xa0 [ 82.811771] [<ffffffff8124da4a>] kernfs_fop_write+0x8a/0x180 [ 82.811787] [<ffffffff811d1023>] __vfs_write+0x23/0xe0 [ 82.811792] [<ffffffff811d1d74>] vfs_write+0xa4/0x190 [ 82.811797] [<ffffffff811d2c14>] SyS_write+0x44/0xb0 [ 82.811801] [<ffffffff817bb81b>] entry_SYSCALL_64_fastpath+0x16/0x73 [ 82.811807] -> #2 (s_active#6){++++.+}: [ 82.811814] [<ffffffff810cc883>] lock_acquire+0xc3/0x1d0 [ 82.811819] [<ffffffff8124c070>] __kernfs_remove+0x210/0x2f0 [ 82.811823] [<ffffffff8124d040>] kernfs_remove_by_name_ns+0x40/0xa0 [ 82.811828] [<ffffffff8124e9e0>] sysfs_remove_file_ns+0x10/0x20 [ 82.811832] [<ffffffff815318d4>] device_del+0x124/0x250 [ 82.811837] [<ffffffff81531a19>] device_unregister+0x19/0x60 [ 82.811841] [<ffffffff8153c051>] cpu_cache_sysfs_exit+0x51/0xb0 [ 82.811846] [<ffffffff8153c628>] cacheinfo_cpu_callback+0x38/0x70 [ 82.811851] [<ffffffff8109ae89>] notifier_call_chain+0x39/0xa0 [ 82.811856] [<ffffffff8109aef9>] __raw_notifier_call_chain+0x9/0x10 [ 82.811860] [<ffffffff810786de>] cpu_notify+0x1e/0x40 [ 82.811865] [<ffffffff81078779>] cpu_notify_nofail+0x9/0x20 [ 82.811869] [<ffffffff81078ac3>] _cpu_down+0x233/0x340 [ 82.811874] [<ffffffff81079019>] disable_nonboot_cpus+0xc9/0x350 [ 82.811878] [<ffffffff810d2e11>] suspend_devices_and_enter+0x5a1/0xb50 [ 82.811883] [<ffffffff810d3903>] pm_suspend+0x543/0x8d0 [ 82.811888] [<ffffffff810d1b77>] state_store+0x77/0xe0 [ 82.811892] [<ffffffff813fa68f>] kobj_attr_store+0xf/0x20 [ 82.811897] [<ffffffff8124e740>] sysfs_kf_write+0x40/0x50 [ 82.811902] [<ffffffff8124dafc>] kernfs_fop_write+0x13c/0x180 [ 82.811906] [<ffffffff811d1023>] __vfs_write+0x23/0xe0 [ 82.811910] [<ffffffff811d1d74>] vfs_write+0xa4/0x190 [ 82.811914] [<ffffffff811d2c14>] SyS_write+0x44/0xb0 [ 82.811918] [<ffffffff817bb81b>] entry_SYSCALL_64_fastpath+0x16/0x73 [ 82.811923] -> #1 (cpu_hotplug.lock){+.+.+.}: [ 82.811929] [<ffffffff810cc883>] lock_acquire+0xc3/0x1d0 [ 82.811933] [<ffffffff817b6f72>] mutex_lock_nested+0x62/0x3b0 [ 82.811940] [<ffffffff810784c1>] get_online_cpus+0x61/0x80 [ 82.811944] [<ffffffff811170eb>] stop_machine+0x1b/0xe0 [ 82.811949] [<ffffffffa0178edd>] gen8_ggtt_insert_entries__BKL+0x2d/0x30 [i915] [ 82.812009] [<ffffffffa017d3a6>] ggtt_bind_vma+0x46/0x70 [i915] [ 82.812045] [<ffffffffa017eb70>] i915_vma_bind+0x140/0x290 [i915] [ 82.812081] [<ffffffffa01862b9>] i915_gem_object_do_pin+0x899/0xb00 [i915] [ 82.812117] [<ffffffffa0186555>] i915_gem_object_pin+0x35/0x40 [i915] [ 82.812154] [<ffffffffa019a23e>] intel_init_pipe_control+0xbe/0x210 [i915] [ 82.812192] [<ffffffffa0197312>] intel_logical_rings_init+0xe2/0xde0 [i915] [ 82.812232] [<ffffffffa0186fe3>] i915_gem_init+0xf3/0x130 [i915] [ 82.812278] [<ffffffffa02097ed>] i915_driver_load+0xf2d/0x1770 [i915] [ 82.812318] [<ffffffff81512474>] drm_dev_register+0xa4/0xb0 [ 82.812323] [<ffffffff8151467e>] drm_get_pci_dev+0xce/0x1e0 [ 82.812328] [<ffffffffa01472cf>] i915_pci_probe+0x2f/0x50 [i915] [ 82.812360] [<ffffffff8143f907>] pci_device_probe+0x87/0xf0 [ 82.812366] [<ffffffff81535f89>] driver_probe_device+0x229/0x450 [ 82.812371] [<ffffffff81536233>] __driver_attach+0x83/0x90 [ 82.812375] [<ffffffff81533c61>] bus_for_each_dev+0x61/0xa0 [ 82.812380] [<ffffffff81535879>] driver_attach+0x19/0x20 [ 82.812384] [<ffffffff8153535f>] bus_add_driver+0x1ef/0x290 [ 82.812388] [<ffffffff81536e9b>] driver_register+0x5b/0xe0 [ 82.812393] [<ffffffff8143e83b>] __pci_register_driver+0x5b/0x60 [ 82.812398] [<ffffffff81514866>] drm_pci_init+0xd6/0x100 [ 82.812402] [<ffffffffa027c094>] 0xffffffffa027c094 [ 82.812406] [<ffffffff810003de>] do_one_initcall+0xae/0x1d0 [ 82.812412] [<ffffffff811595a0>] do_init_module+0x5b/0x1cb [ 82.812417] [<ffffffff81106160>] load_module+0x1c20/0x2480 [ 82.812422] [<ffffffff81106bae>] SyS_finit_module+0x7e/0xa0 [ 82.812428] [<ffffffff817bb81b>] entry_SYSCALL_64_fastpath+0x16/0x73 [ 82.812433] -> #0 (&dev->struct_mutex){+.+.+.}: [ 82.812439] [<ffffffff810cbe59>] __lock_acquire+0x1fc9/0x20f0 [ 82.812443] [<ffffffff810cc883>] lock_acquire+0xc3/0x1d0 [ 82.812456] [<ffffffff8150d9e7>] drm_gem_mmap+0x1c7/0x270 [ 82.812460] [<ffffffff81196a14>] mmap_region+0x334/0x580 [ 82.812466] [<ffffffff81196fc4>] do_mmap+0x364/0x410 [ 82.812470] [<ffffffff8117b38d>] vm_mmap_pgoff+0x6d/0xa0 [ 82.812474] [<ffffffff811950f4>] SyS_mmap_pgoff+0x184/0x220 [ 82.812479] [<ffffffff8100a0fd>] SyS_mmap+0x1d/0x20 [ 82.812484] [<ffffffff817bb81b>] entry_SYSCALL_64_fastpath+0x16/0x73 [ 82.812489] other info that might help us debug this: [ 82.812493] Chain exists of: &dev->struct_mutex --> s_active#6 --> &mm->mmap_sem [ 82.812502] Possible unsafe locking scenario: [ 82.812506] CPU0 CPU1 [ 82.812508] ---- ---- [ 82.812510] lock(&mm->mmap_sem); [ 82.812514] lock(s_active#6); [ 82.812519] lock(&mm->mmap_sem); [ 82.812522] lock(&dev->struct_mutex); [ 82.812526] *** DEADLOCK *** [ 82.812531] 1 lock held by kms_setmode/5859: [ 82.812533] #0: (&mm->mmap_sem){++++++}, at: [<ffffffff8117b364>] vm_mmap_pgoff+0x44/0xa0 [ 82.812541] stack backtrace: [ 82.812547] CPU: 0 PID: 5859 Comm: kms_setmode Not tainted 4.5.0-rc4-gfxbench+ #1 [ 82.812550] Hardware name: /NUC5CPYB, BIOS PYBSWCEL.86A.0040.2015.0814.1353 08/14/2015 [ 82.812553] 0000000000000000 ffff880079407bf0 ffffffff813f8505 ffffffff825fb270 [ 82.812560] ffffffff825c4190 ffff880079407c30 ffffffff810c84ac ffff880079407c90 [ 82.812566] ffff8800797ed328 ffff8800797ecb00 0000000000000001 ffff8800797ed350 [ 82.812573] Call Trace: [ 82.812578] [<ffffffff813f8505>] dump_stack+0x67/0x92 [ 82.812582] [<ffffffff810c84ac>] print_circular_bug+0x1fc/0x310 [ 82.812586] [<ffffffff810cbe59>] __lock_acquire+0x1fc9/0x20f0 [ 82.812590] [<ffffffff810cc883>] lock_acquire+0xc3/0x1d0 [ 82.812594] [<ffffffff8150d9c1>] ? drm_gem_mmap+0x1a1/0x270 [ 82.812599] [<ffffffff8150d9e7>] drm_gem_mmap+0x1c7/0x270 [ 82.812603] [<ffffffff8150d9c1>] ? drm_gem_mmap+0x1a1/0x270 [ 82.812608] [<ffffffff81196a14>] mmap_region+0x334/0x580 [ 82.812612] [<ffffffff81196fc4>] do_mmap+0x364/0x410 [ 82.812616] [<ffffffff8117b38d>] vm_mmap_pgoff+0x6d/0xa0 [ 82.812629] [<ffffffff811950f4>] SyS_mmap_pgoff+0x184/0x220 [ 82.812633] [<ffffffff8100a0fd>] SyS_mmap+0x1d/0x20 [ 82.812637] [<ffffffff817bb81b>] entry_SYSCALL_64_fastpath+0x16/0x73 Highly unlikely though this scenario is, we can avoid the issue entirely by moving the copy operation from out under the kernfs_get_active() tracking by assigning the preallocated buffer its own mutex. The temporary buffer allocation doesn't require mutex locking as it is entirely local. The locked section was extended by the addition of the preallocated buf to speed up md user operations in commit 2b75869b Author: NeilBrown <neilb@suse.de> Date: Mon Oct 13 16:41:28 2014 +1100 sysfs/kernfs: allow attributes to request write buffer be pre-allocated. Reported-by:Ville Syrjälä <ville.syrjala@linux.intel.com> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94350 Signed-off-by:
Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by:
Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: NeilBrown <neilb@suse.de> Acked-by:
Tejun Heo <tj@kernel.org> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
e4234a1f
