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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, "Michel Dänzer" <mdaenzer@redhat.com>,
	"Mark Yacoub" <markyacoub@chromium.org>,
	"Sean Paul" <seanpaul@chromium.org>,
	"Sasha Levin" <sashal@kernel.org>
Subject: [PATCH 4.14 16/23] drm: Copy drm_wait_vblank to user before returning
Date: Wed,  1 Sep 2021 14:27:01 +0200	[thread overview]
Message-ID: <20210901122250.310573095@linuxfoundation.org> (raw)
In-Reply-To: <20210901122249.786673285@linuxfoundation.org>

From: Mark Yacoub <markyacoub@google.com>

[ Upstream commit fa0b1ef5f7a694f48e00804a391245f3471aa155 ]

[Why]
Userspace should get back a copy of drm_wait_vblank that's been modified
even when drm_wait_vblank_ioctl returns a failure.

Rationale:
drm_wait_vblank_ioctl modifies the request and expects the user to read
it back. When the type is RELATIVE, it modifies it to ABSOLUTE and updates
the sequence to become current_vblank_count + sequence (which was
RELATIVE), but now it became ABSOLUTE.
drmWaitVBlank (in libdrm) expects this to be the case as it modifies
the request to be Absolute so it expects the sequence to would have been
updated.

The change is in compat_drm_wait_vblank, which is called by
drm_compat_ioctl. This change of copying the data back regardless of the
return number makes it en par with drm_ioctl, which always copies the
data before returning.

[How]
Return from the function after everything has been copied to user.

Fixes IGT:kms_flip::modeset-vs-vblank-race-interruptible
Tested on ChromeOS Trogdor(msm)

Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Signed-off-by: Mark Yacoub <markyacoub@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210812194917.1703356-1-markyacoub@chromium.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/drm_ioc32.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_ioc32.c b/drivers/gpu/drm/drm_ioc32.c
index 86105e7f07fc..6773e8f09fc3 100644
--- a/drivers/gpu/drm/drm_ioc32.c
+++ b/drivers/gpu/drm/drm_ioc32.c
@@ -855,8 +855,6 @@ static int compat_drm_wait_vblank(struct file *file, unsigned int cmd,
 	req.request.sequence = req32.request.sequence;
 	req.request.signal = req32.request.signal;
 	err = drm_ioctl_kernel(file, drm_wait_vblank_ioctl, &req, DRM_UNLOCKED);
-	if (err)
-		return err;
 
 	req32.reply.type = req.reply.type;
 	req32.reply.sequence = req.reply.sequence;
@@ -865,7 +863,7 @@ static int compat_drm_wait_vblank(struct file *file, unsigned int cmd,
 	if (copy_to_user(argp, &req32, sizeof(req32)))
 		return -EFAULT;
 
-	return 0;
+	return err;
 }
 
 #if defined(CONFIG_X86)
-- 
2.30.2




  parent reply	other threads:[~2021-09-01 12:29 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-01 12:26 [PATCH 4.14 00/23] 4.14.246-rc1 review Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 01/23] ARC: Fix CONFIG_STACKDEPOT Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 02/23] can: usb: esd_usb2: esd_usb2_rx_event(): fix the interchange of the CAN RX and TX error counters Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 03/23] Revert "USB: serial: ch341: fix character loss at high transfer rates" Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 04/23] USB: serial: option: add new VID/PID to support Fibocom FG150 Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 05/23] usb: dwc3: gadget: Fix dwc3_calc_trbs_left() Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 06/23] usb: dwc3: gadget: Stop EP0 transfers during pullup disable Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 07/23] IB/hfi1: Fix possible null-pointer dereference in _extend_sdma_tx_descs() Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 08/23] e1000e: Fix the max snoop/no-snoop latency for 10M Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 09/23] ip_gre: add validation for csum_start Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 10/23] xgene-v2: Fix a resource leak in the error handling path of xge_probe() Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 11/23] net: marvell: fix MVNETA_TX_IN_PRGRS bit number Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 12/23] usb: gadget: u_audio: fix race condition on endpoint stop Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 13/23] opp: remove WARN when no valid OPPs remain Greg Kroah-Hartman
2021-09-01 12:26 ` [PATCH 4.14 14/23] virtio: Improve vq->broken access to avoid any compiler optimization Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 15/23] vringh: Use wiov->used to check for read/write desc order Greg Kroah-Hartman
2021-09-01 12:27 ` Greg Kroah-Hartman [this message]
2021-09-01 12:27 ` [PATCH 4.14 17/23] drm/nouveau/disp: power down unused DP links during init Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 18/23] net/rds: dma_map_sg is entitled to merge entries Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 19/23] vt_kdsetmode: extend console locking Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 20/23] fbmem: add margin check to fb_check_caps() Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 21/23] KVM: x86/mmu: Treat NX as used (not reserved) for all !TDP shadow MMUs Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 22/23] KVM: X86: MMU: Use the correct inherited permissions to get shadow page Greg Kroah-Hartman
2021-09-01 12:27 ` [PATCH 4.14 23/23] Revert "floppy: reintroduce O_NDELAY fix" Greg Kroah-Hartman
2021-09-01 19:21 ` [PATCH 4.14 00/23] 4.14.246-rc1 review Jon Hunter
2021-09-01 19:22 ` Jon Hunter
2021-09-02  1:08 ` Samuel Zou
2021-09-02 16:08 ` Naresh Kamboju
2021-09-02 21:50 ` Guenter Roeck

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