tree 2508c41e97ef71b47abfdcf27109c4024ab83cab
parent 50b5f55ba2b75c80c32daa5ed1e5ad6d8532d957
author Andy Lutomirski <luto@kernel.org> 1612035781 -0800
committer Andy Lutomirski <luto@kernel.org> 1612936989 -0800

x86/fault: Don't run fixups for SMAP violations

A SMAP-violating kernel access is not a recoverable condition.  Imagine
kernel code that, outside of a uaccess region, dereferences a pointer to
the user range by accident.  If SMAP is on, this will reliably generate
as an intentional user access.  This makes it easy for bugs to be
overlooked if code is inadequately tested both with and without SMAP.

We discovered this because BPF can generate invalid accesses to user
memory, but those warnings only got printed if SMAP was off.  With this
patch, this type of error will be discovered with SMAP on as well.

Cc: Yonghong Song <yhs@fb.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andy Lutomirski <luto@kernel.org>