drm/atomic: If the atomic check fails, return its value first

mlankhorst · mlankhorst · commit a0ffc51e20e9 · 2017-08-15T12:38:05.000+02:00
The last part of drm_atomic_check_only is testing whether we need to fail with -EINVAL when modeset is not allowed, but forgets to return the value when atomic_check() fails first. This results in -EDEADLK being replaced by -EINVAL, and the sanity check in drm_modeset_drop_locks kicks in: [ 308.531734] ------------[ cut here ]------------ [ 308.531791] WARNING: CPU: 0 PID: 1886 at drivers/gpu/drm/drm_modeset_lock.c:217 drm_modeset_drop_locks+0x33/0xc0 [drm] [ 308.531828] Modules linked in: [ 308.532050] CPU: 0 PID: 1886 Comm: kms_atomic Tainted: G U W 4.13.0-rc5-patser+ #5225 [ 308.532082] Hardware name: NUC5i7RYB, BIOS RYBDWi35.86A.0246.2015.0309.1355 03/09/2015 [ 308.532124] task: ffff8800cd9dae00 task.stack: ffff8800ca3b8000 [ 308.532168] RIP: 0010:drm_modeset_drop_locks+0x33/0xc0 [drm] [ 308.532189] RSP: 0018:ffff8800ca3bf980 EFLAGS: 00010282 [ 308.532211] RAX: dffffc0000000000 RBX: ffff8800ca3bfaf8 RCX: 0000000013a171e6 [ 308.532235] RDX: 1ffff10019477f69 RSI: ffffffffa8ba4fa0 RDI: ffff8800ca3bfb48 [ 308.532258] RBP: ffff8800ca3bf998 R08: 0000000000000000 R09: 0000000000000003 [ 308.532281] R10: 0000000079dbe066 R11: 00000000f760b34b R12: 0000000000000001 [ 308.532304] R13: dffffc0000000000 R14: 00000000ffffffea R15: ffff880096889680 [ 308.532328] FS: 00007ff00959cec0(0000) GS:ffff8800d4e00000(0000) knlGS:0000000000000000 [ 308.532359] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 308.532380] CR2: 0000000000000008 CR3: 00000000ca2e3000 CR4: 00000000003406f0 [ 308.532402] Call Trace: [ 308.532440] drm_mode_atomic_ioctl+0x19fa/0x1c00 [drm] [ 308.532488] ? drm_atomic_set_property+0x1220/0x1220 [drm] [ 308.532565] ? avc_has_extended_perms+0xc39/0xff0 [ 308.532593] ? lock_downgrade+0x610/0x610 [ 308.532640] ? drm_atomic_set_property+0x1220/0x1220 [drm] [ 308.532680] drm_ioctl_kernel+0x154/0x1a0 [drm] [ 308.532755] drm_ioctl+0x624/0x8f0 [drm] [ 308.532858] ? drm_atomic_set_property+0x1220/0x1220 [drm] [ 308.532976] ? drm_getunique+0x210/0x210 [drm] [ 308.533061] do_vfs_ioctl+0xd92/0xe40 [ 308.533121] ? ioctl_preallocate+0x1b0/0x1b0 [ 308.533160] ? selinux_capable+0x20/0x20 [ 308.533191] ? do_fcntl+0x1b1/0xbf0 [ 308.533219] ? kasan_slab_free+0xa2/0xb0 [ 308.533249] ? f_getown+0x4b/0xa0 [ 308.533278] ? putname+0xcf/0xe0 [ 308.533309] ? security_file_ioctl+0x57/0x90 [ 308.533342] SyS_ioctl+0x4e/0x80 [ 308.533374] entry_SYSCALL_64_fastpath+0x18/0xad [ 308.533405] RIP: 0033:0x7ff00779e4d7 [ 308.533431] RSP: 002b:00007fff66a043d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 308.533481] RAX: ffffffffffffffda RBX: 000000e7c7ca5910 RCX: 00007ff00779e4d7 [ 308.533560] RDX: 00007fff66a04430 RSI: 00000000c03864bc RDI: 0000000000000003 [ 308.533608] RBP: 00007ff007a5fb00 R08: 000000e7c7ca4620 R09: 000000e7c7ca5e60 [ 308.533647] R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000070 [ 308.533685] R13: 0000000000000000 R14: 0000000000000000 R15: 000000e7c7ca5930 [ 308.533770] Code: ff df 55 48 89 e5 41 55 41 54 53 48 89 fb 48 83 c7 50 48 89 fa 48 c1 ea 03 80 3c 02 00 74 05 e8 94 d4 16 e7 48 83 7b 50 00 74 02 <0f> ff 4c 8d 6b 58 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 [ 308.534086] ---[ end trace 77f11e53b1df44ad ]--- Solve this by adding the missing return. This is also a bugfix because we could end up rejecting updates with -EINVAL because of a early -EDEADLK, while if atomic_check ran to completion it might have downgraded the modeset to a fastset. Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Testcase: kms_atomic Link: https://patchwork.freedesktop.org/patch/msgid/20170815095706.23624-1-maarten.lankhorst@linux.intel.com Fixes: d34f20d ("drm: Atomic modeset ioctl") Cc: <stable@vger.kernel.org> # v4.0+ Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
@@ -1655,6 +1655,9 @@ int drm_atomic_check_only(struct drm_atomic_state *state)
 	if (config->funcs->atomic_check)
 		ret = config->funcs->atomic_check(state->dev, state);
 
+	if (ret)
+		return ret;
+
 	if (!state->allow_modeset) {
 		for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
 			if (drm_atomic_crtc_needs_modeset(crtc_state)) {
@@ -1665,7 +1668,7 @@ int drm_atomic_check_only(struct drm_atomic_state *state)
 		}
 	}
 
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL(drm_atomic_check_only);
 

Original file line number	Diff line number	Diff line change
`@@ -1655,6 +1655,9 @@ int drm_atomic_check_only(struct drm_atomic_state *state)`
`1655`	`1655`	`if (config->funcs->atomic_check)`
`1656`	`1656`	`ret = config->funcs->atomic_check(state->dev, state);`
`1657`	`1657`
	`1658`	`+ if (ret)`
	`1659`	`+ return ret;`
	`1660`	`+`
`1658`	`1661`	`if (!state->allow_modeset) {`
`1659`	`1662`	`for_each_new_crtc_in_state(state, crtc, crtc_state, i) {`
`1660`	`1663`	`if (drm_atomic_crtc_needs_modeset(crtc_state)) {`
`@@ -1665,7 +1668,7 @@ int drm_atomic_check_only(struct drm_atomic_state *state)`
`1665`	`1668`	`}`
`1666`	`1669`	`}`
`1667`	`1670`
`1668`		`- return ret;`
	`1671`	`+ return 0;`
`1669`	`1672`	`}`
`1670`	`1673`	`EXPORT_SYMBOL(drm_atomic_check_only);`
`1671`	`1674`