Alexander Kapshuk
2020-Oct-09 18:11 UTC
[Nouveau] [PATCH] drm/nouveau/kms: Fix NULL pointer dereference in nouveau_connector_detect_depth
This oops manifests itself on the following hardware:
01:00.0 VGA compatible controller: NVIDIA Corporation G98M [GeForce G 103M] (rev
a1)
Oct 09 14:17:46 lp-sasha kernel: BUG: kernel NULL pointer dereference, address:
0000000000000000
Oct 09 14:17:46 lp-sasha kernel: #PF: supervisor read access in kernel mode
Oct 09 14:17:46 lp-sasha kernel: #PF: error_code(0x0000) - not-present page
Oct 09 14:17:46 lp-sasha kernel: PGD 0 P4D 0
Oct 09 14:17:46 lp-sasha kernel: Oops: 0000 [#1] SMP PTI
Oct 09 14:17:46 lp-sasha kernel: CPU: 1 PID: 191 Comm: systemd-udevd Not tainted
5.9.0-rc8-next-20201009 #38
Oct 09 14:17:46 lp-sasha kernel: Hardware name: Hewlett-Packard Compaq Presario
CQ61 Notebook PC/306A, BIOS F.03 03/23/2009
Oct 09 14:17:46 lp-sasha kernel: RIP:
0010:nouveau_connector_detect_depth+0x71/0xc0 [nouveau]
Oct 09 14:17:46 lp-sasha kernel: Code: 0a 00 00 48 8b 49 48 c7 87 b8 00 00 00 06
00 00 00 80 b9 4d 0a 00 00 00 75 1e 83 fa 41 75 05 48 85 c0 75 29 8b 81 10 0d 00
00 <39> 06 7c 25 f6 81 14 0d 00 00 02 75 b7 c3 80 b9 0c 0d 00 00 00 75
Oct 09 14:17:46 lp-sasha kernel: RSP: 0018:ffffc9000028f8c0 EFLAGS: 00010297
Oct 09 14:17:46 lp-sasha kernel: RAX: 0000000000014c08 RBX: ffff8880369d4000
RCX: ffff8880369d3000
Oct 09 14:17:46 lp-sasha kernel: RDX: 0000000000000040 RSI: 0000000000000000
RDI: ffff8880369d4000
Oct 09 14:17:46 lp-sasha kernel: RBP: ffff88800601cc00 R08: ffff8880051da298
R09: ffffffff8226201a
Oct 09 14:17:46 lp-sasha kernel: R10: ffff88800469aa80 R11: ffff888004c84ff8
R12: 0000000000000000
Oct 09 14:17:46 lp-sasha kernel: R13: ffff8880051da000 R14: 0000000000002000
R15: 0000000000000003
Oct 09 14:17:46 lp-sasha kernel: FS: 00007fd0192b3440(0000)
GS:ffff8880bc900000(0000) knlGS:0000000000000000
Oct 09 14:17:46 lp-sasha kernel: CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
Oct 09 14:17:46 lp-sasha kernel: CR2: 0000000000000000 CR3: 0000000004976000
CR4: 00000000000006e0
Oct 09 14:17:46 lp-sasha kernel: Call Trace:
Oct 09 14:17:46 lp-sasha kernel: nouveau_connector_get_modes+0x1e6/0x240
[nouveau]
Oct 09 14:17:46 lp-sasha kernel: ? kfree+0xb9/0x240
Oct 09 14:17:46 lp-sasha kernel: ? drm_connector_list_iter_next+0x7c/0xa0
Oct 09 14:17:46 lp-sasha kernel:
drm_helper_probe_single_connector_modes+0x1ba/0x7c0
Oct 09 14:17:46 lp-sasha kernel: drm_client_modeset_probe+0x27e/0x1360
Oct 09 14:17:46 lp-sasha kernel: ? nvif_object_sclass_put+0xc/0x20 [nouveau]
Oct 09 14:17:46 lp-sasha kernel: ? nouveau_cli_init+0x3cc/0x440 [nouveau]
Oct 09 14:17:46 lp-sasha kernel: ? ktime_get_mono_fast_ns+0x49/0xa0
Oct 09 14:17:46 lp-sasha kernel: ? nouveau_drm_open+0x4e/0x180 [nouveau]
Oct 09 14:17:46 lp-sasha kernel:
__drm_fb_helper_initial_config_and_unlock+0x3f/0x4a0
Oct 09 14:17:46 lp-sasha kernel: ? drm_file_alloc+0x18f/0x260
Oct 09 14:17:46 lp-sasha kernel: ? mutex_lock+0x9/0x40
Oct 09 14:17:46 lp-sasha kernel: ? drm_client_init+0x110/0x160
Oct 09 14:17:46 lp-sasha kernel: nouveau_fbcon_init+0x14d/0x1c0 [nouveau]
Oct 09 14:17:46 lp-sasha kernel: nouveau_drm_device_init+0x1c0/0x880 [nouveau]
Oct 09 14:17:46 lp-sasha kernel: nouveau_drm_probe+0x11a/0x1e0 [nouveau]
Oct 09 14:17:46 lp-sasha kernel: pci_device_probe+0xcd/0x140
Oct 09 14:17:46 lp-sasha kernel: really_probe+0xd8/0x400
Oct 09 14:17:46 lp-sasha kernel: driver_probe_device+0x4a/0xa0
Oct 09 14:17:46 lp-sasha kernel: device_driver_attach+0x9c/0xc0
Oct 09 14:17:46 lp-sasha kernel: __driver_attach+0x6f/0x100
Oct 09 14:17:46 lp-sasha kernel: ? device_driver_attach+0xc0/0xc0
Oct 09 14:17:46 lp-sasha kernel: bus_for_each_dev+0x75/0xc0
Oct 09 14:17:46 lp-sasha kernel: bus_add_driver+0x106/0x1c0
Oct 09 14:17:46 lp-sasha kernel: driver_register+0x86/0xe0
Oct 09 14:17:46 lp-sasha kernel: ? 0xffffffffa044e000
Oct 09 14:17:46 lp-sasha kernel: do_one_initcall+0x48/0x1e0
Oct 09 14:17:46 lp-sasha kernel: ? _cond_resched+0x11/0x60
Oct 09 14:17:46 lp-sasha kernel: ? kmem_cache_alloc_trace+0x19c/0x1e0
Oct 09 14:17:46 lp-sasha kernel: do_init_module+0x57/0x220
Oct 09 14:17:46 lp-sasha kernel: __do_sys_finit_module+0xa0/0xe0
Oct 09 14:17:46 lp-sasha kernel: do_syscall_64+0x33/0x40
Oct 09 14:17:46 lp-sasha kernel: entry_SYSCALL_64_after_hwframe+0x44/0xa9
Oct 09 14:17:46 lp-sasha kernel: RIP: 0033:0x7fd01a060d5d
Oct 09 14:17:46 lp-sasha kernel: Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3
0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f
05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e3 70 0c 00 f7 d8 64 89 01 48
Oct 09 14:17:46 lp-sasha kernel: RSP: 002b:00007ffc8ad38a98 EFLAGS: 00000246
ORIG_RAX: 0000000000000139
Oct 09 14:17:46 lp-sasha kernel: RAX: ffffffffffffffda RBX: 0000563f6e7fd530
RCX: 00007fd01a060d5d
Oct 09 14:17:46 lp-sasha kernel: RDX: 0000000000000000 RSI: 00007fd01a19f95d
RDI: 000000000000000f
Oct 09 14:17:46 lp-sasha kernel: RBP: 0000000000020000 R08: 0000000000000000
R09: 0000000000000007
Oct 09 14:17:46 lp-sasha kernel: R10: 000000000000000f R11: 0000000000000246
R12: 00007fd01a19f95d
Oct 09 14:17:46 lp-sasha kernel: R13: 0000000000000000 R14: 0000563f6e7fbc10
R15: 0000563f6e7fd530
Oct 09 14:17:46 lp-sasha kernel: Modules linked in: nouveau(+) ttm xt_string
xt_mark xt_LOG vgem v4l2_dv_timings uvcvideo ulpi udf ts_kmp ts_fsm ts_bm
snd_aloop sil164 qat_dh895xccvf nf_nat_sip nf_nat_irc nf_nat_ftp nf_nat
nf_log_ipv6 nf_log_ipv4 nf_log_common ltc2990 lcd intel_qat input_leds i2c_mux
gspca_main videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_common
videodev mc drivetemp cuse fuse crc_itu_t coretemp ch7006 ath5k ath algif_hash
Oct 09 14:17:46 lp-sasha kernel: CR2: 0000000000000000
Oct 09 14:17:46 lp-sasha kernel: ---[ end trace 0ddafe218ad30017 ]---
Oct 09 14:17:46 lp-sasha kernel: RIP:
0010:nouveau_connector_detect_depth+0x71/0xc0 [nouveau]
Oct 09 14:17:46 lp-sasha kernel: Code: 0a 00 00 48 8b 49 48 c7 87 b8 00 00 00 06
00 00 00 80 b9 4d 0a 00 00 00 75 1e 83 fa 41 75 05 48 85 c0 75 29 8b 81 10 0d 00
00 <39> 06 7c 25 f6 81 14 0d 00 00 02 75 b7 c3 80 b9 0c 0d 00 00 00 75
Oct 09 14:17:46 lp-sasha kernel: RSP: 0018:ffffc9000028f8c0 EFLAGS: 00010297
Oct 09 14:17:46 lp-sasha kernel: RAX: 0000000000014c08 RBX: ffff8880369d4000
RCX: ffff8880369d3000
Oct 09 14:17:46 lp-sasha kernel: RDX: 0000000000000040 RSI: 0000000000000000
RDI: ffff8880369d4000
Oct 09 14:17:46 lp-sasha kernel: RBP: ffff88800601cc00 R08: ffff8880051da298
R09: ffffffff8226201a
Oct 09 14:17:46 lp-sasha kernel: R10: ffff88800469aa80 R11: ffff888004c84ff8
R12: 0000000000000000
Oct 09 14:17:46 lp-sasha kernel: R13: ffff8880051da000 R14: 0000000000002000
R15: 0000000000000003
Oct 09 14:17:46 lp-sasha kernel: FS: 00007fd0192b3440(0000)
GS:ffff8880bc900000(0000) knlGS:0000000000000000
Oct 09 14:17:46 lp-sasha kernel: CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
Oct 09 14:17:46 lp-sasha kernel: CR2: 0000000000000000 CR3: 0000000004976000
CR4: 00000000000006e0
The disassembly:
Code: 0a 00 00 48 8b 49 48 c7 87 b8 00 00 00 06 00 00 00 80 b9 4d 0a 00 00 00 75
1e 83 fa 41 75 05 48 85 c0 75 29 8b 81 10 0d 00 00 <39> 06 7c 25 f6 81 14
0d 00 00 02 75 b7 c3 80 b9 0c 0d 00 00 00 75
All code
======= 0: 0a 00 or (%rax),%al
2: 00 48 8b add %cl,-0x75(%rax)
5: 49 rex.WB
6: 48 c7 87 b8 00 00 00 movq $0x6,0xb8(%rdi)
d: 06 00 00 00
11: 80 b9 4d 0a 00 00 00 cmpb $0x0,0xa4d(%rcx)
18: 75 1e jne 0x38
1a: 83 fa 41 cmp $0x41,%edx
1d: 75 05 jne 0x24
1f: 48 85 c0 test %rax,%rax
22: 75 29 jne 0x4d
24: 8b 81 10 0d 00 00 mov 0xd10(%rcx),%eax
2a:* 39 06 cmp %eax,(%rsi) <-- trapping
instruction
2c: 7c 25 jl 0x53
2e: f6 81 14 0d 00 00 02 testb $0x2,0xd14(%rcx)
35: 75 b7 jne 0xffffffffffffffee
37: c3 retq
38: 80 b9 0c 0d 00 00 00 cmpb $0x0,0xd0c(%rcx)
3f: 75 .byte 0x75
Code starting with the faulting instruction
========================================== 0: 39 06 cmp
%eax,(%rsi)
2: 7c 25 jl 0x29
4: f6 81 14 0d 00 00 02 testb $0x2,0xd14(%rcx)
b: 75 b7 jne 0xffffffffffffffc4
d: c3 retq
e: 80 b9 0c 0d 00 00 00 cmpb $0x0,0xd0c(%rcx)
15: 75 .byte 0x75
objdump -SF --disassemble=nouveau_connector_detect_depth
[...]
if (nv_connector->edid &&
c85e1: 83 fa 41 cmp $0x41,%edx
c85e4: 75 05 jne c85eb
<nouveau_connector_detect_depth+0x6b> (File Offset: 0xc866b)
c85e6: 48 85 c0 test %rax,%rax
c85e9: 75 29 jne c8614
<nouveau_connector_detect_depth+0x94> (File Offset: 0xc8694)
nv_connector->type == DCB_CONNECTOR_LVDS_SPWG)
duallink = ((u8 *)nv_connector->edid)[121] == 2;
else
duallink = mode->clock >=
bios->fp.duallink_transition_clk;
if ((!duallink && (bios->fp.strapless_is_24bit & 1)) ||
c85eb: 8b 81 10 0d 00 00 mov 0xd10(%rcx),%eax
c85f1: 39 06 cmp %eax,(%rsi)
c85f3: 7c 25 jl c861a
<nouveau_connector_detect_depth+0x9a> (File Offset: 0xc869a)
( duallink && (bios->fp.strapless_is_24bit & 2)))
c85f5: f6 81 14 0d 00 00 02 testb $0x2,0xd14(%rcx)
c85fc: 75 b7 jne c85b5
<nouveau_connector_detect_depth+0x35> (File Offset: 0xc8635)
connector->display_info.bpc = 8;
[...]
% scripts/faddr2line
/lib/modules/5.9.0-rc8-next-20201009/kernel/drivers/gpu/drm/nouveau/nouveau.ko
nouveau_connector_detect_depth+0x71/0xc0
nouveau_connector_detect_depth+0x71/0xc0:
nouveau_connector_detect_depth at
/home/sasha/linux-next/drivers/gpu/drm/nouveau/nouveau_connector.c:891
It is actually line 889. See the disassembly above.
889 duallink = mode->clock >=
bios->fp.duallink_transition_clk;
The NULL pointer being dereferenced is mode.
Git bisect has identified the following commit as bad:
f28e32d3906e drm/nouveau/kms: Don't change EDID when it hasn't actually
changed
Here is the chain of events that causes the oops.
On entry to nouveau_connector_detect_lvds, edid is set to NULL.
The call to nouveau_connector_detect sets nv_connector->edid to valid
memory, with status being set to connector_status_connected and the flow
of execution branching to the out label.
The subsequent call to nouveau_connector_set_edid erronously clears
nv_connector->edid, via the local edid pointer which remains set to NULL.
Fix this by setting edid to the value of the just acquired
nv_connector->edid and call nouveau_connector_set_edid in the out label
only if nv_connector->edid and edid point to different memory addresses
thus preventing nv_connector->edid from being turned into a dangling
pointer.
Fixes: f28e32d3906e ("drm/nouveau/kms: Don't change EDID when it
hasn't actually changed")
Signed-off-by: Alexander Kapshuk <alexander.kapshuk at gmail.com>
---
drivers/gpu/drm/nouveau/nouveau_connector.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c
b/drivers/gpu/drm/nouveau/nouveau_connector.c
index 49dd0cbc332f..a3f53d2ac86e 100644
--- a/drivers/gpu/drm/nouveau/nouveau_connector.c
+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
@@ -669,8 +669,10 @@ nouveau_connector_detect_lvds(struct drm_connector
*connector, bool force)
/* Try retrieving EDID via DDC */
if (!drm->vbios.fp_no_ddc) {
status = nouveau_connector_detect(connector, force);
- if (status == connector_status_connected)
+ if (status == connector_status_connected) {
+ edid = nv_connector->edid;
goto out;
+ }
}
/* On some laptops (Sony, i'm looking at you) there appears to
@@ -720,7 +722,8 @@ nouveau_connector_detect_lvds(struct drm_connector
*connector, bool force)
status = connector_status_unknown;
#endif
- nouveau_connector_set_edid(nv_connector, edid);
+ if (nv_connector->edid != edid)
+ nouveau_connector_set_edid(nv_connector, edid);
nouveau_connector_set_encoder(connector, nv_encoder);
return status;
}
--
2.28.0
Lyude Paul
2020-Oct-12 21:30 UTC
[Nouveau] [PATCH] drm/nouveau/kms: Fix NULL pointer dereference in nouveau_connector_detect_depth
Hi! Thanks for the catch, just one comment down below On Fri, 2020-10-09 at 21:11 +0300, Alexander Kapshuk wrote:> This oops manifests itself on the following hardware: > 01:00.0 VGA compatible controller: NVIDIA Corporation G98M [GeForce G 103M] > (rev a1) > > Oct 09 14:17:46 lp-sasha kernel: BUG: kernel NULL pointer dereference, > address: 0000000000000000 > Oct 09 14:17:46 lp-sasha kernel: #PF: supervisor read access in kernel mode > Oct 09 14:17:46 lp-sasha kernel: #PF: error_code(0x0000) - not-present page > Oct 09 14:17:46 lp-sasha kernel: PGD 0 P4D 0 > Oct 09 14:17:46 lp-sasha kernel: Oops: 0000 [#1] SMP PTI > Oct 09 14:17:46 lp-sasha kernel: CPU: 1 PID: 191 Comm: systemd-udevd Not > tainted 5.9.0-rc8-next-20201009 #38 > Oct 09 14:17:46 lp-sasha kernel: Hardware name: Hewlett-Packard Compaq > Presario CQ61 Notebook PC/306A, BIOS F.03 03/23/2009 > Oct 09 14:17:46 lp-sasha kernel: RIP: > 0010:nouveau_connector_detect_depth+0x71/0xc0 [nouveau] > Oct 09 14:17:46 lp-sasha kernel: Code: 0a 00 00 48 8b 49 48 c7 87 b8 00 00 00 > 06 00 00 00 80 b9 4d 0a 00 00 00 75 1e 83 fa 41 75 05 48 85 c0 75 29 8b 81 10 > 0d 00 00 <39> 06 7c 25 f6 81 14 0d 00 00 02 75 b7 c3 80 b9 0c 0d 00 00 00 75 > Oct 09 14:17:46 lp-sasha kernel: RSP: 0018:ffffc9000028f8c0 EFLAGS: 00010297 > Oct 09 14:17:46 lp-sasha kernel: RAX: 0000000000014c08 RBX: ffff8880369d4000 > RCX: ffff8880369d3000 > Oct 09 14:17:46 lp-sasha kernel: RDX: 0000000000000040 RSI: 0000000000000000 > RDI: ffff8880369d4000 > Oct 09 14:17:46 lp-sasha kernel: RBP: ffff88800601cc00 R08: ffff8880051da298 > R09: ffffffff8226201a > Oct 09 14:17:46 lp-sasha kernel: R10: ffff88800469aa80 R11: ffff888004c84ff8 > R12: 0000000000000000 > Oct 09 14:17:46 lp-sasha kernel: R13: ffff8880051da000 R14: 0000000000002000 > R15: 0000000000000003 > Oct 09 14:17:46 lp-sasha kernel: FS: 00007fd0192b3440(0000) > GS:ffff8880bc900000(0000) knlGS:0000000000000000 > Oct 09 14:17:46 lp-sasha kernel: CS: 0010 DS: 0000 ES: 0000 CR0: > 0000000080050033 > Oct 09 14:17:46 lp-sasha kernel: CR2: 0000000000000000 CR3: 0000000004976000 > CR4: 00000000000006e0 > Oct 09 14:17:46 lp-sasha kernel: Call Trace: > Oct 09 14:17:46 lp-sasha kernel: nouveau_connector_get_modes+0x1e6/0x240 > [nouveau] > Oct 09 14:17:46 lp-sasha kernel: ? kfree+0xb9/0x240 > Oct 09 14:17:46 lp-sasha kernel: ? drm_connector_list_iter_next+0x7c/0xa0 > Oct 09 14:17:46 lp-sasha > kernel: drm_helper_probe_single_connector_modes+0x1ba/0x7c0 > Oct 09 14:17:46 lp-sasha kernel: drm_client_modeset_probe+0x27e/0x1360 > Oct 09 14:17:46 lp-sasha kernel: ? nvif_object_sclass_put+0xc/0x20 [nouveau] > Oct 09 14:17:46 lp-sasha kernel: ? nouveau_cli_init+0x3cc/0x440 [nouveau] > Oct 09 14:17:46 lp-sasha kernel: ? ktime_get_mono_fast_ns+0x49/0xa0 > Oct 09 14:17:46 lp-sasha kernel: ? nouveau_drm_open+0x4e/0x180 [nouveau] > Oct 09 14:17:46 lp-sasha > kernel: __drm_fb_helper_initial_config_and_unlock+0x3f/0x4a0 > Oct 09 14:17:46 lp-sasha kernel: ? drm_file_alloc+0x18f/0x260 > Oct 09 14:17:46 lp-sasha kernel: ? mutex_lock+0x9/0x40 > Oct 09 14:17:46 lp-sasha kernel: ? drm_client_init+0x110/0x160 > Oct 09 14:17:46 lp-sasha kernel: nouveau_fbcon_init+0x14d/0x1c0 [nouveau] > Oct 09 14:17:46 lp-sasha kernel: nouveau_drm_device_init+0x1c0/0x880 > [nouveau] > Oct 09 14:17:46 lp-sasha kernel: nouveau_drm_probe+0x11a/0x1e0 [nouveau] > Oct 09 14:17:46 lp-sasha kernel: pci_device_probe+0xcd/0x140 > Oct 09 14:17:46 lp-sasha kernel: really_probe+0xd8/0x400 > Oct 09 14:17:46 lp-sasha kernel: driver_probe_device+0x4a/0xa0 > Oct 09 14:17:46 lp-sasha kernel: device_driver_attach+0x9c/0xc0 > Oct 09 14:17:46 lp-sasha kernel: __driver_attach+0x6f/0x100 > Oct 09 14:17:46 lp-sasha kernel: ? device_driver_attach+0xc0/0xc0 > Oct 09 14:17:46 lp-sasha kernel: bus_for_each_dev+0x75/0xc0 > Oct 09 14:17:46 lp-sasha kernel: bus_add_driver+0x106/0x1c0 > Oct 09 14:17:46 lp-sasha kernel: driver_register+0x86/0xe0 > Oct 09 14:17:46 lp-sasha kernel: ? 0xffffffffa044e000 > Oct 09 14:17:46 lp-sasha kernel: do_one_initcall+0x48/0x1e0 > Oct 09 14:17:46 lp-sasha kernel: ? _cond_resched+0x11/0x60 > Oct 09 14:17:46 lp-sasha kernel: ? kmem_cache_alloc_trace+0x19c/0x1e0 > Oct 09 14:17:46 lp-sasha kernel: do_init_module+0x57/0x220 > Oct 09 14:17:46 lp-sasha kernel: __do_sys_finit_module+0xa0/0xe0 > Oct 09 14:17:46 lp-sasha kernel: do_syscall_64+0x33/0x40 > Oct 09 14:17:46 lp-sasha kernel: entry_SYSCALL_64_after_hwframe+0x44/0xa9 > Oct 09 14:17:46 lp-sasha kernel: RIP: 0033:0x7fd01a060d5d > Oct 09 14:17:46 lp-sasha kernel: Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 > f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 > 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e3 70 0c 00 f7 d8 64 89 01 48 > Oct 09 14:17:46 lp-sasha kernel: RSP: 002b:00007ffc8ad38a98 EFLAGS: 00000246 > ORIG_RAX: 0000000000000139 > Oct 09 14:17:46 lp-sasha kernel: RAX: ffffffffffffffda RBX: 0000563f6e7fd530 > RCX: 00007fd01a060d5d > Oct 09 14:17:46 lp-sasha kernel: RDX: 0000000000000000 RSI: 00007fd01a19f95d > RDI: 000000000000000f > Oct 09 14:17:46 lp-sasha kernel: RBP: 0000000000020000 R08: 0000000000000000 > R09: 0000000000000007 > Oct 09 14:17:46 lp-sasha kernel: R10: 000000000000000f R11: 0000000000000246 > R12: 00007fd01a19f95d > Oct 09 14:17:46 lp-sasha kernel: R13: 0000000000000000 R14: 0000563f6e7fbc10 > R15: 0000563f6e7fd530 > Oct 09 14:17:46 lp-sasha kernel: Modules linked in: nouveau(+) ttm xt_string > xt_mark xt_LOG vgem v4l2_dv_timings uvcvideo ulpi udf ts_kmp ts_fsm ts_bm > snd_aloop sil164 qat_dh895xccvf nf_nat_sip nf_nat_irc nf_nat_ftp nf_nat > nf_log_ipv6 nf_log_ipv4 nf_log_common ltc2990 lcd intel_qat input_leds i2c_mux > gspca_main videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_common > videodev mc drivetemp cuse fuse crc_itu_t coretemp ch7006 ath5k ath algif_hash > Oct 09 14:17:46 lp-sasha kernel: CR2: 0000000000000000 > Oct 09 14:17:46 lp-sasha kernel: ---[ end trace 0ddafe218ad30017 ]--- > Oct 09 14:17:46 lp-sasha kernel: RIP: > 0010:nouveau_connector_detect_depth+0x71/0xc0 [nouveau] > Oct 09 14:17:46 lp-sasha kernel: Code: 0a 00 00 48 8b 49 48 c7 87 b8 00 00 00 > 06 00 00 00 80 b9 4d 0a 00 00 00 75 1e 83 fa 41 75 05 48 85 c0 75 29 8b 81 10 > 0d 00 00 <39> 06 7c 25 f6 81 14 0d 00 00 02 75 b7 c3 80 b9 0c 0d 00 00 00 75 > Oct 09 14:17:46 lp-sasha kernel: RSP: 0018:ffffc9000028f8c0 EFLAGS: 00010297 > Oct 09 14:17:46 lp-sasha kernel: RAX: 0000000000014c08 RBX: ffff8880369d4000 > RCX: ffff8880369d3000 > Oct 09 14:17:46 lp-sasha kernel: RDX: 0000000000000040 RSI: 0000000000000000 > RDI: ffff8880369d4000 > Oct 09 14:17:46 lp-sasha kernel: RBP: ffff88800601cc00 R08: ffff8880051da298 > R09: ffffffff8226201a > Oct 09 14:17:46 lp-sasha kernel: R10: ffff88800469aa80 R11: ffff888004c84ff8 > R12: 0000000000000000 > Oct 09 14:17:46 lp-sasha kernel: R13: ffff8880051da000 R14: 0000000000002000 > R15: 0000000000000003 > Oct 09 14:17:46 lp-sasha kernel: FS: 00007fd0192b3440(0000) > GS:ffff8880bc900000(0000) knlGS:0000000000000000 > Oct 09 14:17:46 lp-sasha kernel: CS: 0010 DS: 0000 ES: 0000 CR0: > 0000000080050033 > Oct 09 14:17:46 lp-sasha kernel: CR2: 0000000000000000 CR3: 0000000004976000 > CR4: 00000000000006e0 > > The disassembly: > Code: 0a 00 00 48 8b 49 48 c7 87 b8 00 00 00 06 00 00 00 80 b9 4d 0a 00 00 00 > 75 1e 83 fa 41 75 05 48 85 c0 75 29 8b 81 10 0d 00 00 <39> 06 7c 25 f6 81 14 > 0d 00 00 02 75 b7 c3 80 b9 0c 0d 00 00 00 75 > All code > =======> 0: 0a 00 or (%rax),%al > 2: 00 48 8b add %cl,-0x75(%rax) > 5: 49 rex.WB > 6: 48 c7 87 b8 00 00 00 movq $0x6,0xb8(%rdi) > d: 06 00 00 00 > 11: 80 b9 4d 0a 00 00 00 cmpb $0x0,0xa4d(%rcx) > 18: 75 1e jne 0x38 > 1a: 83 fa 41 cmp $0x41,%edx > 1d: 75 05 jne 0x24 > 1f: 48 85 c0 test %rax,%rax > 22: 75 29 jne 0x4d > 24: 8b 81 10 0d 00 00 mov 0xd10(%rcx),%eax > 2a:* 39 06 cmp %eax,(%rsi) <-- trapping > instruction > 2c: 7c 25 jl 0x53 > 2e: f6 81 14 0d 00 00 02 testb $0x2,0xd14(%rcx) > 35: 75 b7 jne 0xffffffffffffffee > 37: c3 retq > 38: 80 b9 0c 0d 00 00 00 cmpb $0x0,0xd0c(%rcx) > 3f: 75 .byte 0x75 > > Code starting with the faulting instruction > ==========================================> 0: 39 06 cmp %eax,(%rsi) > 2: 7c 25 jl 0x29 > 4: f6 81 14 0d 00 00 02 testb $0x2,0xd14(%rcx) > b: 75 b7 jne 0xffffffffffffffc4 > d: c3 retq > e: 80 b9 0c 0d 00 00 00 cmpb $0x0,0xd0c(%rcx) > 15: 75 .byte 0x75 > > objdump -SF --disassemble=nouveau_connector_detect_depth > [...] > if (nv_connector->edid && > c85e1: 83 fa 41 cmp $0x41,%edx > c85e4: 75 05 jne c85eb > <nouveau_connector_detect_depth+0x6b> (File Offset: 0xc866b) > c85e6: 48 85 c0 test %rax,%rax > c85e9: 75 29 jne c8614 > <nouveau_connector_detect_depth+0x94> (File Offset: 0xc8694) > nv_connector->type == DCB_CONNECTOR_LVDS_SPWG) > duallink = ((u8 *)nv_connector->edid)[121] == 2; > else > duallink = mode->clock >= bios->fp.duallink_transition_clk; > > if ((!duallink && (bios->fp.strapless_is_24bit & 1)) || > c85eb: 8b 81 10 0d 00 00 mov 0xd10(%rcx),%eax > c85f1: 39 06 cmp %eax,(%rsi) > c85f3: 7c 25 jl c861a > <nouveau_connector_detect_depth+0x9a> (File Offset: 0xc869a) > ( duallink && (bios->fp.strapless_is_24bit & 2))) > c85f5: f6 81 14 0d 00 00 02 testb $0x2,0xd14(%rcx) > c85fc: 75 b7 jne c85b5 > <nouveau_connector_detect_depth+0x35> (File Offset: 0xc8635) > connector->display_info.bpc = 8; > [...] > > % scripts/faddr2line /lib/modules/5.9.0-rc8-next- > 20201009/kernel/drivers/gpu/drm/nouveau/nouveau.ko > nouveau_connector_detect_depth+0x71/0xc0 > nouveau_connector_detect_depth+0x71/0xc0: > nouveau_connector_detect_depth at /home/sasha/linux- > next/drivers/gpu/drm/nouveau/nouveau_connector.c:891 > > It is actually line 889. See the disassembly above. > 889 duallink = mode->clock >= bios- > >fp.duallink_transition_clk; > > The NULL pointer being dereferenced is mode. > > Git bisect has identified the following commit as bad: > f28e32d3906e drm/nouveau/kms: Don't change EDID when it hasn't actually > changed > > Here is the chain of events that causes the oops. > On entry to nouveau_connector_detect_lvds, edid is set to NULL. > The call to nouveau_connector_detect sets nv_connector->edid to valid > memory, with status being set to connector_status_connected and the flow > of execution branching to the out label. > > The subsequent call to nouveau_connector_set_edid erronously clears > nv_connector->edid, via the local edid pointer which remains set to NULL. > > Fix this by setting edid to the value of the just acquired > nv_connector->edid and call nouveau_connector_set_edid in the out label > only if nv_connector->edid and edid point to different memory addresses > thus preventing nv_connector->edid from being turned into a dangling > pointer. > > Fixes: f28e32d3906e ("drm/nouveau/kms: Don't change EDID when it hasn't > actually changed") > Signed-off-by: Alexander Kapshuk <alexander.kapshuk at gmail.com> > --- > drivers/gpu/drm/nouveau/nouveau_connector.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c > b/drivers/gpu/drm/nouveau/nouveau_connector.c > index 49dd0cbc332f..a3f53d2ac86e 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_connector.c > +++ b/drivers/gpu/drm/nouveau/nouveau_connector.c > @@ -669,8 +669,10 @@ nouveau_connector_detect_lvds(struct drm_connector > *connector, bool force) > /* Try retrieving EDID via DDC */ > if (!drm->vbios.fp_no_ddc) { > status = nouveau_connector_detect(connector, force); > - if (status == connector_status_connected) > + if (status == connector_status_connected) { > + edid = nv_connector->edid; > goto out; > + } > } > > /* On some laptops (Sony, i'm looking at you) there appears to > @@ -720,7 +722,8 @@ nouveau_connector_detect_lvds(struct drm_connector > *connector, bool force) > status = connector_status_unknown; > #endif > > - nouveau_connector_set_edid(nv_connector, edid); > + if (nv_connector->edid != edid) > + nouveau_connector_set_edid(nv_connector, edid);Could we just update nouveau_connector_set_edid() to do the (nv_connector->edid != edid) check instead of open coding it here? With that fixed: Reviewed-by: Lyude Paul <lyude at redhat.com>> nouveau_connector_set_encoder(connector, nv_encoder); > return status; > } > -- > 2.28.0 >-- Sincerely, Lyude Paul (she/her) Software Engineer at Red Hat
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