This is a note to let you know that I've just added the patch titled
drm/shmem-helper: Fix BUG_ON() on mmap(PROT_WRITE, MAP_PRIVATE)
to the 6.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-shmem-helper-fix-bug_on-on-mmap-prot_write-map_private.patch
and it can be found in the queue-6.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 39bc27bd688066a63e56f7f64ad34fae03fbe3b8 Mon Sep 17 00:00:00 2001
From: "Wachowski, Karol" <[email protected]>
Date: Mon, 20 May 2024 12:05:14 +0200
Subject: drm/shmem-helper: Fix BUG_ON() on mmap(PROT_WRITE, MAP_PRIVATE)
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From: Wachowski, Karol <[email protected]>
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 <[email protected]>
Cc: Eric Anholt <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Cc: Maxime Ripard <[email protected]>
Cc: Thomas Zimmermann <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: [email protected]
Cc: <[email protected]> # v5.2+
Signed-off-by: Wachowski, Karol <[email protected]>
Signed-off-by: Jacek Lawrynowicz <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
Link:
https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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);
Patches currently in stable-queue which might be from [email protected]
are
queue-6.9/drm-shmem-helper-fix-bug_on-on-mmap-prot_write-map_private.patch
