[PATCH] drm/i915/gvt: Fix the validation on size field of dp aux header

[changbin.du at intel.com]

From: Changbin Du <changbin.du at intel.com>

The assertion for len is wrong, so fix it. And for where to validate
user input, we should not warn by call trace.

[ 290.584739] WARNING: CPU: 0 PID: 1471 at drivers/gpu/drm/i915/gvt/handlers.c:969 dp_aux_ch_ctl_mmio_write+0x394/0x430 [i915]
[ 290.586113] task: ffff880111fe8000 task.stack: ffffc90044a9c000
[ 290.586192] RIP: e030:dp_aux_ch_ctl_mmio_write+0x394/0x430 [i915]
[ 290.586258] RSP: e02b:ffffc90044a9fd88 EFLAGS: 00010282
[ 290.586315] RAX: 0000000000000017 RBX: 0000000000000003 RCX: ffffffff82461148
[ 290.586391] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000201
[ 290.586468] RBP: ffffc90043ed1000 R08: 0000000000000248 R09: 00000000000003d8
[ 290.586544] R10: ffffc90044bdd314 R11: 0000000000000011 R12: 0000000000064310
[ 290.586621] R13: 00000000fe4003ff R14: ffffc900432d1008 R15: ffff88010fa7cb40
[ 290.586701] FS: 0000000000000000(0000) GS:ffff880123200000(0000) knlGS:0000000000000000
[ 290.586787] CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 290.586849] CR2: 00007f67ea44e000 CR3: 0000000116078000 CR4: 0000000000042660
[ 290.586926] Call Trace:
[ 290.586958] ? __switch_to_asm+0x40/0x70
[ 290.587017] intel_vgpu_mmio_reg_rw+0x1ec/0x3c0 [i915]
[ 290.587087] intel_vgpu_emulate_mmio_write+0xa8/0x2c0 [i915]
[ 290.587151] xengt_emulation_thread+0x501/0x7a0 [xengt]
[ 290.587208] ? __schedule+0x3c6/0x890
[ 290.587250] ? wait_woken+0x80/0x80
[ 290.587290] kthread+0xfc/0x130
[ 290.587326] ? xengt_gpa_to_va+0x1f0/0x1f0 [xengt]
[ 290.587378] ? kthread_create_on_node+0x70/0x70
[ 290.587429] ? do_group_exit+0x3a/0xa0
[ 290.587471] ret_from_fork+0x35/0x40

Signed-off-by: Changbin Du <changbin.du at intel.com>
---
 drivers/gpu/drm/i915/gvt/display.h  |  2 +-
 drivers/gpu/drm/i915/gvt/handlers.c | 13 +++++++++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/display.h b/drivers/gpu/drm/i915/gvt/display.h
index b46b868..ea7c1c5 100644
--- a/drivers/gpu/drm/i915/gvt/display.h
+++ b/drivers/gpu/drm/i915/gvt/display.h
@@ -67,7 +67,7 @@
 #define AUX_NATIVE_REPLY_NAK    (0x1 << 4)
 #define AUX_NATIVE_REPLY_DEFER  (0x2 << 4)
 
-#define AUX_BURST_SIZE          16
+#define AUX_BURST_SIZE          20
 
 /* DPCD addresses */
 #define DPCD_REV			0x000
diff --git a/drivers/gpu/drm/i915/gvt/handlers.c b/drivers/gpu/drm/i915/gvt/handlers.c
index a33c1c3e..b77adcc 100644
--- a/drivers/gpu/drm/i915/gvt/handlers.c
+++ b/drivers/gpu/drm/i915/gvt/handlers.c
@@ -900,11 +900,14 @@ static int dp_aux_ch_ctl_mmio_write(struct intel_vgpu *vgpu,
 		}
 
 		/*
-		 * Write request format: (command + address) occupies
-		 * 3 bytes, followed by (len + 1) bytes of data.
+		 * Write request format: Headr (command + address + size) occupies
+		 * 4 bytes, followed by (len + 1) bytes of data. See details at
+		 * intel_dp_aux_transfer().
 		 */
-		if (WARN_ON((len + 4) > AUX_BURST_SIZE))
+		if ((len + 1 + 4) > AUX_BURST_SIZE) {
+			gvt_vgpu_err("dp_aux_header: len %d is too large\n", len);
 			return -EINVAL;
+		}
 
 		/* unpack data from vreg to buf */
 		for (t = 0; t < 4; t++) {
@@ -968,8 +971,10 @@ static int dp_aux_ch_ctl_mmio_write(struct intel_vgpu *vgpu,
 		/*
 		 * Read reply format: ACK (1 byte) plus (len + 1) bytes of data.
 		 */
-		if (WARN_ON((len + 2) > AUX_BURST_SIZE))
+		if ((len + 2) > AUX_BURST_SIZE) {
+			gvt_vgpu_err("dp_aux_header: len %d is too large\n", len);
 			return -EINVAL;
+		}
 
 		/* read from virtual DPCD to vreg */
 		/* first 4 bytes: [ACK][addr][addr+1][addr+2] */
-- 
2.7.4