From: Andy Lutomirski Date: Wed, 10 Feb 2021 02:33:45 +0000 (-0800) Subject: x86/fault: Don't run fixups for SMAP violations X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=ca247283781d754216395a41c5e8be8ec79a5f1c;p=linux.git 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. This was discovered because BPF can generate invalid accesses to user memory, but those warnings only got printed if SMAP was off. Make it so that this type of error will be discovered with SMAP on as well. [ bp: Massage commit message. ] Signed-off-by: Andy Lutomirski Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/66a02343624b1ff46f02a838c497fc05c1a871b3.1612924255.git.luto@kernel.org --- diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 1a0cfede88220..1c3054bb4a5b2 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1279,9 +1279,12 @@ void do_user_addr_fault(struct pt_regs *regs, */ if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) && !(error_code & X86_PF_USER) && - !(regs->flags & X86_EFLAGS_AC))) - { - bad_area_nosemaphore(regs, error_code, address); + !(regs->flags & X86_EFLAGS_AC))) { + /* + * No extable entry here. This was a kernel access to an + * invalid pointer. get_kernel_nofault() will not get here. + */ + page_fault_oops(regs, error_code, address); return; }