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Subject[PATCH] drm/fb-helper: only unmap if buffer not null
Date
drm_fbdev_cleanup() can be called when fb_helper->buffer is null, hence
fb_helper->buffer should be checked before calling
drm_client_buffer_vunmap(). This buffer is also checked in
drm_client_framebuffer_delete(), so we should also do the same thing for
drm_client_buffer_vunmap().

[ 199.128742] RIP: 0010:drm_client_buffer_vunmap+0xd/0x20
[ 199.129031] Code: 43 18 48 8b 53 20 49 89 45 00 49 89 55 08 5b 44 89 e0 41 5c 41 5d 41 5e 5d
c3 0f 1f 00 53 48 89 fb 48 8d 7f 10 e8 73 7d a1 ff <48> 8b 7b 10 48 8d 73 18 5b e9 75 53 fc ff 0
f 1f 44 00 00 48 b8 00
[ 199.130041] RSP: 0018:ffff888103f3fc88 EFLAGS: 00010282
[ 199.130329] RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff8214d46d
[ 199.130733] RDX: 1ffffffff079c6b9 RSI: 0000000000000246 RDI: ffffffff83ce35c8
[ 199.131119] RBP: ffff888103d25458 R08: 0000000000000001 R09: fffffbfff0791761
[ 199.131505] R10: ffffffff83c8bb07 R11: fffffbfff0791760 R12: 0000000000000000
[ 199.131891] R13: ffff888103d25468 R14: ffff888103d25418 R15: ffff888103f18120
[ 199.132277] FS: 00007f36fdcbb6a0(0000) GS:ffff88815b400000(0000) knlGS:0000000000000000
[ 199.132721] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 199.133033] CR2: 0000000000000010 CR3: 0000000103d26000 CR4: 00000000000006f0
[ 199.133420] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 199.133807] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 199.134195] Call Trace:
[ 199.134333] drm_fbdev_cleanup+0x179/0x1a0
[ 199.134562] drm_fbdev_client_unregister+0x2b/0x40
[ 199.134828] drm_client_dev_unregister+0xa8/0x180
[ 199.135088] drm_dev_unregister+0x61/0x110
[ 199.135315] mgag200_pci_remove+0x38/0x52 [mgag200]
[ 199.135586] pci_device_remove+0x62/0xe0
[ 199.135806] device_release_driver_internal+0x148/0x270
[ 199.136094] driver_detach+0x76/0xe0
[ 199.136294] bus_remove_driver+0x7e/0x100
[ 199.136521] pci_unregister_driver+0x28/0xf0
[ 199.136759] __x64_sys_delete_module+0x268/0x300
[ 199.137016] ? __ia32_sys_delete_module+0x300/0x300
[ 199.137285] ? call_rcu+0x3e4/0x580
[ 199.137481] ? fpregs_assert_state_consistent+0x4d/0x60
[ 199.137767] ? exit_to_user_mode_prepare+0x2f/0x130
[ 199.138037] do_syscall_64+0x33/0x40
[ 199.138237] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 199.138517] RIP: 0033:0x7f36fdc3dcf7

Signed-off-by: Tong Zhang <ztong0001@gmail.com>
---
drivers/gpu/drm/drm_fb_helper.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index b9a616737c0e..f6baa2046124 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -2048,7 +2048,7 @@ static void drm_fbdev_cleanup(struct drm_fb_helper *fb_helper)

if (shadow)
vfree(shadow);
- else
+ else if (fb_helper->buffer)
drm_client_buffer_vunmap(fb_helper->buffer);

drm_client_framebuffer_delete(fb_helper->buffer);
--
2.25.1
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