Re: [PATCH] drm/i915: Remove redundant user_access_end() from __copy_from_user() error path

[Thomas Gleixner]

On Thu, 25 Jul 2019, Josh Poimboeuf wrote:

> Objtool reports:
> 
>   drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x36: redundant UACCESS disable
> 
> __copy_from_user() already does both STAC and CLAC, so the
> user_access_end() in its error path adds an extra unnecessary CLAC.
> 
> Fixes: 0b2c8f8b6b0c ("i915: fix missing user_access_end() in page fault exception case")
> Reported-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Reported-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Tested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
> Link: https://github.com/ClangBuiltLinux/linux/issues/617
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>

Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>