From: Mark Yacoub markyacoub@google.com
mainline inclusion from mainline-5.10.62 commit 6fd6e20520ccd05a1ac3321404dd498cc28576cb bugzilla: 182217 https://gitee.com/openeuler/kernel/issues/I4EFOS
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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[ 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-marky... Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Chen Jun chenjun102@huawei.com Acked-by: Weilong Chen chenweilong@huawei.com
Signed-off-by: Chen Jun chenjun102@huawei.com --- 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 dc734d4828a1..aaf8d625ce1a 100644 --- a/drivers/gpu/drm/drm_ioc32.c +++ b/drivers/gpu/drm/drm_ioc32.c @@ -865,8 +865,6 @@ 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; @@ -875,7 +873,7 @@ 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)