[55/63] drm: Fix use-after-free in drm_gem_vm_close()

From: Greg KH
Date: Fri Mar 25 2011 - 19:56:52 EST

2.6.38-stable review patch. If anyone has any objections, please let us know.

------------------

From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

commit b74ad5ae14def5e81ad0be3dddb96e485b861b1b upstream.

As we may release the last reference, we need to store the device in a
local variable in order to unlock afterwards.

[ 60.140768] BUG: unable to handle kernel paging request at 6b6b6b9f
[ 60.140973] IP: [<c1536d11>] __mutex_unlock_slowpath+0x5a/0x111
[ 60.141014] *pdpt = 0000000024a54001 *pde = 0000000000000000
[ 60.141014] Oops: 0002 [#1] PREEMPT SMP
[ 60.141014] last sysfs file: /sys/devices/LNXSYSTM:00/device:00/PNP0A08:00/PNP0C0A:00/power_supply/BAT0/voltage_now
[ 60.141014] Modules linked in: uvcvideo ath9k pegasus ath9k_common ath9k_hw hid_egalax ath3k joydev asus_laptop sparse_keymap battery input_polldev
[ 60.141014]
[ 60.141014] Pid: 771, comm: meego-ux-daemon Not tainted 2.6.37.2-7.1 #1 EXOPC EXOPG06411/EXOPG06411
[ 60.141014] EIP: 0060:[<c1536d11>] EFLAGS: 00010046 CPU: 0
[ 60.141014] EIP is at __mutex_unlock_slowpath+0x5a/0x111
[ 60.141014] EAX: 00000100 EBX: 6b6b6b9b ECX: e9b4a1b0 EDX: e4a4e580
[ 60.141014] ESI: db162558 EDI: 00000246 EBP: e480be50 ESP: e480be44
[ 60.141014] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
[ 60.141014] Process meego-ux-daemon (pid: 771, ti=e480a000 task=e9b4a1b0 task.ti=e480a000)
[ 60.141014] Stack:
[ 60.141014] e4a4e580 db162558 f5a2f838 e480be58 c1536dd0 e480be68 c125ab1b db162558
[ 60.141014] db1624e0 e480be78 c10ba071 db162558 f760241c e480be94 c10bb0bc 000155fe
[ 60.141014] f760241c f5a2f838 f5a2f8c8 00000000 e480bea4 c1037c24 00000000 f5a2f838
[ 60.141014] Call Trace:
[ 60.141014] [<c1536dd0>] ? mutex_unlock+0x8/0xa
[ 60.141014] [<c125ab1b>] ? drm_gem_vm_close+0x39/0x3d
[ 60.141014] [<c10ba071>] ? remove_vma+0x2d/0x58
[ 60.141014] [<c10bb0bc>] ? exit_mmap+0x126/0x13f
[ 60.141014] [<c1037c24>] ? mmput+0x37/0x9a
[ 60.141014] [<c10d450d>] ? exec_mmap+0x178/0x19c
[ 60.141014] [<c1537f85>] ? _raw_spin_unlock+0x1d/0x36
[ 60.141014] [<c10d4eb0>] ? flush_old_exec+0x42/0x75
[ 60.141014] [<c1104442>] ? load_elf_binary+0x32a/0x922
[ 60.141014] [<c10d3f76>] ? search_binary_handler+0x200/0x2ea
[ 60.141014] [<c10d3ecf>] ? search_binary_handler+0x159/0x2ea
[ 60.141014] [<c1104118>] ? load_elf_binary+0x0/0x922
[ 60.141014] [<c10d56b2>] ? do_execve+0x1ff/0x2e6
[ 60.141014] [<c100970e>] ? sys_execve+0x2d/0x55
[ 60.141014] [<c1002a5a>] ? ptregs_execve+0x12/0x18
[ 60.141014] [<c10029dc>] ? sysenter_do_call+0x12/0x3c
[ 60.141014] [<c1530000>] ? init_centaur+0x9c/0x1ba
[ 60.141014] Code: c1 00 75 0f ba 38 01 00 00 b8 8c 3a 6c c1 e8 cc 2e b0 ff 9c 58 8d 74 26 00 89 c7 fa 90 8d 74 26 00 e8 d2 b4 b2 ff b8 00 01 00 00 <f0> 66 0f c1 43 04 38 e0 74 07 f3 90 8a 43 04 eb f5 83 3d 64 ef
[ 60.141014] EIP: [<c1536d11>] __mutex_unlock_slowpath+0x5a/0x111 SS:ESP 0068:e480be44
[ 60.141014] CR2: 000000006b6b6b9f

Reported-by: Rusty Lynch <rusty.lynch@xxxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
drivers/gpu/drm/drm_gem.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -498,11 +498,12 @@ EXPORT_SYMBOL(drm_gem_vm_open);
void drm_gem_vm_close(struct vm_area_struct *vma)
{
struct drm_gem_object *obj = vma->vm_private_data;
+ struct drm_device *dev = obj->dev;

- mutex_lock(&obj->dev->struct_mutex);
+ mutex_lock(&dev->struct_mutex);
drm_vm_close_locked(vma);
drm_gem_object_unreference(obj);
- mutex_unlock(&obj->dev->struct_mutex);
+ mutex_unlock(&dev->struct_mutex);
}
EXPORT_SYMBOL(drm_gem_vm_close);



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