* [PATCH 6.9 257/281] drm/shmem-helper: Fix BUG_ON() on mmap(PROT_WRITE, MAP_PRIVATE)
[not found] <20240619125609.836313103@linuxfoundation.org>
@ 2024-06-19 12:56 ` Greg Kroah-Hartman
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From: Greg Kroah-Hartman @ 2024-06-19 12:56 UTC (permalink / raw)
To: stable
Cc: Greg Kroah-Hartman, patches, Noralf Trønnes, Eric Anholt,
Rob Herring, Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann,
David Airlie, Daniel Vetter, dri-devel, Wachowski, Karol,
Jacek Lawrynowicz, Daniel Vetter, Wachowski
6.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Wachowski, Karol <karol.wachowski@intel.com>
commit 39bc27bd688066a63e56f7f64ad34fae03fbe3b8 upstream.
Lack of check for copy-on-write (COW) mapping in drm_gem_shmem_mmap
allows users to call mmap with PROT_WRITE and MAP_PRIVATE flag
causing a kernel panic due to BUG_ON in vmf_insert_pfn_prot:
BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
Return -EINVAL early if COW mapping is detected.
This bug affects all drm drivers using default shmem helpers.
It can be reproduced by this simple example:
void *ptr = mmap(0, size, PROT_WRITE, MAP_PRIVATE, fd, mmap_offset);
ptr[0] = 0;
Fixes: 2194a63a818d ("drm: Add library for shmem backed GEM objects")
Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: Eric Anholt <eric@anholt.net>
Cc: Rob Herring <robh@kernel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v5.2+
Signed-off-by: Wachowski, Karol <karol.wachowski@intel.com>
Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20240520100514.925681-1-jacek.lawrynowicz@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/drm_gem_shmem_helper.c | 3 +++
1 file changed, 3 insertions(+)
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -610,6 +610,9 @@ int drm_gem_shmem_mmap(struct drm_gem_sh
return ret;
}
+ if (is_cow_mapping(vma->vm_flags))
+ return -EINVAL;
+
dma_resv_lock(shmem->base.resv, NULL);
ret = drm_gem_shmem_get_pages(shmem);
dma_resv_unlock(shmem->base.resv);
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