Re: [PATCH] [v2] ubsan: build ubsan.c more conservatively

[Andrey Ryabinin]

On 7/22/19 3:50 PM, Arnd Bergmann wrote:
> objtool points out several conditions that it does not like, depending
> on the combination with other configuration options and compiler
> variants:
> 
> stack protector:
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0xbf: call to __stack_chk_fail() with UACCESS enabled
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0xbe: call to __stack_chk_fail() with UACCESS enabled
> 
> stackleak plugin:
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0x4a: call to stackleak_track_stack() with UACCESS enabled
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0x4a: call to stackleak_track_stack() with UACCESS enabled
> 
> kasan:
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0x25: call to memcpy() with UACCESS enabled
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0x25: call to memcpy() with UACCESS enabled
> 
> The stackleak and kasan options just need to be disabled for this file
> as we do for other files already. For the stack protector, we already
> attempt to disable it, but this fails on clang because the check is
> mixed with the gcc specific -fno-conserve-stack option. According
> to Andrey Ryabinin, that option is not even needed, dropping it here
> fixes the stackprotector issue.
> 
> Fixes: d08965a27e84 ("x86/uaccess, ubsan: Fix UBSAN vs. SMAP")
> Link: https://lore.kernel.org/lkml/20190617123109.667090-1-arnd@xxxxxxxx/t/
> Link: https://lore.kernel.org/lkml/20190722091050.2188664-1-arnd@xxxxxxxx/t/
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>


Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>