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| author | Jason Ekstrand <jason@jlekstrand.net> | 2021-07-08 10:48:25 -0500 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2021-07-08 19:47:31 +0200 |
| commit | def25b7bc342d7eb6643408300127404608d3df2 (patch) | |
| tree | c40539b36ea38f63267adea0f58152e54ac3b23e /drivers/gpu/drm/i915/gem/i915_gem_context.c | |
| parent | bc2ceb7a08758357ed2ff1d876dc9d60bdefb080 (diff) | |
| download | linux-def25b7bc342d7eb6643408300127404608d3df2.tar.bz2 | |
drm/i915/gem: Make an alignment check more sensible
What we really want to check is that size of the engines array, i.e.
args->size - sizeof(*user) is divisible by the element size, i.e.
sizeof(*user->engines) because that's what's required for computing the
array length right below the check. However, we're currently not doing
this and instead doing a compile-time check that sizeof(*user) is
divisible by sizeof(*user->engines) and avoiding the subtraction. As
far as I can tell, the only reason for the more confusing pair of checks
is to avoid a single subtraction of a constant.
The other thing the BUILD_BUG_ON might be trying to implicitly check is
that offsetof(user->engines) == sizeof(*user) and we don't have any
weird padding throwing us off. However, that's not the check it's doing
and it's not even a reliable way to do that check.
Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210708154835.528166-21-jason@jlekstrand.net
Diffstat (limited to 'drivers/gpu/drm/i915/gem/i915_gem_context.c')
| -rw-r--r-- | drivers/gpu/drm/i915/gem/i915_gem_context.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c index 3c59d1e4080c..f135fbc97c5a 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c @@ -1723,9 +1723,8 @@ set_engines(struct i915_gem_context *ctx, goto replace; } - BUILD_BUG_ON(!IS_ALIGNED(sizeof(*user), sizeof(*user->engines))); if (args->size < sizeof(*user) || - !IS_ALIGNED(args->size, sizeof(*user->engines))) { + !IS_ALIGNED(args->size - sizeof(*user), sizeof(*user->engines))) { drm_dbg(&i915->drm, "Invalid size for engine array: %d\n", args->size); return -EINVAL; |