pci_get_class(class, from) drops the refcount for 'from', so the
extra pci_dev_put we do on it will result in a use after free bug
sometime later starting with the WARN below.
Regression introduced in
commit 6a9c4b35e6696a63805b6da5e4889c6986e9ee1b
Author: Rui Guo <firemeteor@xxxxxxxxxxxxxxxxxxxxx>
Date: Wed Jun 19 21:10:23 2013 +0800
drm/i915: Fix PCH detect with multiple ISA bridges in VM
[ 164.338460] WARNING: CPU: 1 PID: 2094 at include/linux/kref.h:47 klist_next+0xae/0x110()
[ 164.347731] CPU: 1 PID: 2094 Comm: modprobe Tainted: G O 3.13.0-imre+ #354
[ 164.356468] Hardware name: Intel Corp. VALLEYVIEW B0 PLATFORM/NOTEBOOK, BIOS BYTICRB1.X64.0062.R70.1310112051 10/11/2013
[ 164.368796] Call Trace:
[ 164.371609] [<ffffffff816a32a6>] dump_stack+0x4e/0x7a
[ 164.377447] [<ffffffff8104f75d>] warn_slowpath_common+0x7d/0xa0
[ 164.384238] [<ffffffff8104f83a>] warn_slowpath_null+0x1a/0x20
[ 164.390851] [<ffffffff8169aeae>] klist_next+0xae/0x110
[ 164.396777] [<ffffffff8130a110>] ? pci_do_find_bus+0x70/0x70
[ 164.403286] [<ffffffff813cb4a9>] bus_find_device+0x89/0xc0
[ 164.409719] [<ffffffff8130a373>] pci_get_dev_by_id+0x63/0xa0
[ 164.416238] [<ffffffff8130a4e4>] pci_get_class+0x44/0x50
[ 164.422433] [<ffffffffa034821f>] intel_dsm_detect+0x16f/0x1f0 [i915]
[ 164.429801] [<ffffffffa03482ae>] intel_register_dsm_handler+0xe/0x10 [i915]
[ 164.437831] [<ffffffffa02d30fe>] i915_driver_load+0xafe/0xf30 [i915]
[ 164.445126] [<ffffffff8158a150>] ? intel_alloc_coherent+0x110/0x110
[ 164.452340] [<ffffffffa0148c07>] drm_dev_register+0xc7/0x150 [drm]
[ 164.459462] [<ffffffffa014b23f>] drm_get_pci_dev+0x11f/0x1f0 [drm]
[ 164.466554] [<ffffffff816abb81>] ? _raw_spin_unlock_irqrestore+0x51/0x70
[ 164.474287] [<ffffffffa02cf7a6>] i915_pci_probe+0x56/0x60 [i915]
[ 164.481185] [<ffffffff8130a028>] pci_device_probe+0x78/0xf0
[ 164.487603] [<ffffffff813cd495>] driver_probe_device+0x155/0x350
[ 164.494505] [<ffffffff813cd74e>] __driver_attach+0x6e/0xa0
[ 164.500826] [<ffffffff813cd6e0>] ? __device_attach+0x50/0x50
[ 164.507333] [<ffffffff813cb2be>] bus_for_each_dev+0x6e/0xc0
[ 164.513752] [<ffffffff813ccefe>] driver_attach+0x1e/0x20
[ 164.519870] [<ffffffff813cc958>] bus_add_driver+0x138/0x260
[ 164.526289] [<ffffffffa0188000>] ? 0xffffffffa0187fff
[ 164.532116] [<ffffffff813cde78>] driver_register+0x98/0xe0
[ 164.538558] [<ffffffffa0188000>] ? 0xffffffffa0187fff
[ 164.544389] [<ffffffff813087b0>] __pci_register_driver+0x60/0x70
[ 164.551336] [<ffffffffa014b37d>] drm_pci_init+0x6d/0x120 [drm]
[ 164.558040] [<ffffffffa0188000>] ? 0xffffffffa0187fff
[ 164.563928] [<ffffffffa018806a>] i915_init+0x6a/0x6c [i915]
[ 164.570363] [<ffffffff810002da>] do_one_initcall+0xaa/0x160
[ 164.576783] [<ffffffff8103b140>] ? set_memory_nx+0x40/0x50
[ 164.583100] [<ffffffff810ce7f5>] load_module+0x1fb5/0x2550
[ 164.589410] [<ffffffff810caab0>] ? store_uevent+0x40/0x40
[ 164.595628] [<ffffffff810cee7d>] SyS_init_module+0xed/0x100
[ 164.602048] [<ffffffff816b3c52>] system_call_fastpath+0x16/0x1b
Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_drv.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 2d05d7c..4e4fc0c 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -347,7 +347,6 @@ void intel_detect_pch(struct drm_device *dev)
*/
pch = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, NULL);
while (pch) {
- struct pci_dev *curr = pch;
if (pch->vendor == PCI_VENDOR_ID_INTEL) {
unsigned short id;
id = pch->device & INTEL_PCH_DEVICE_ID_MASK;
@@ -385,15 +384,15 @@ void intel_detect_pch(struct drm_device *dev)
} else {
goto check_next;
}
- pci_dev_put(pch);
break;
}
check_next:
- pch = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, curr);
- pci_dev_put(curr);
+ pch = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, pch);
}
if (!pch)
DRM_DEBUG_KMS("No PCH found?\n");
+ else
+ pci_dev_put(pch);
}
bool i915_semaphore_is_enabled(struct drm_device *dev)
--
1.8.4
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