Mesa (main): i965: export GEM handle with RDWR access rights

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Module: Mesa
Branch: main
Commit: 5eaf8b59c858bc93f0b18045f49dcdfe6b1d6e75
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=5eaf8b59c858bc93f0b18045f49dcdfe6b1d6e75

Author: Maksim Sisov <msisov at igalia.com>
Date:   Tue May 18 08:23:56 2021 +0300

i965: export GEM handle with RDWR access rights

There is a regression that made it impossible to export gem
handles with write access.

That is, a client may export gem handles of each buffer plane, then
export dmabuf fds using these handles, and mmap these dmabuf in
a different process (this is what Chromium does).

After https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4861,
it became impossible as mmap resulted in EACCESS error as slightly
different approach was taken for exporting these gem handles.

This CL fixes exporting gem handles (which are exported from dmabuf
fds) by adding the DRM_RDWR flag.

Cc: mesa-stable

Fixes #3119

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10850>

---

 src/mesa/drivers/dri/i965/brw_bufmgr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.c b/src/mesa/drivers/dri/i965/brw_bufmgr.c
index 2c423a27dc4..bed6ca9e2ea 100644
--- a/src/mesa/drivers/dri/i965/brw_bufmgr.c
+++ b/src/mesa/drivers/dri/i965/brw_bufmgr.c
@@ -1581,7 +1581,7 @@ brw_bo_gem_export_to_prime(struct brw_bo *bo, int *prime_fd)
    brw_bo_make_external(bo);
 
    if (drmPrimeHandleToFD(bufmgr->fd, bo->gem_handle,
-                          DRM_CLOEXEC, prime_fd) != 0)
+                          DRM_CLOEXEC | DRM_RDWR, prime_fd) != 0)
       return -errno;
 
    bo->reusable = false;