mirrors
/
linux-stable
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
1
0
Fork 0
Code Issues Releases Wiki Activity

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 <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/66a02343624b1ff46f02a838c497fc05c1a871b3.1612924255.git.luto@kernel.org
This commit is contained in:
Andy Lutomirski 2021-02-09 18:33:45 -08:00 committed by Borislav Petkov
parent 66fcd98883
commit ca24728378
1 changed files with 6 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
arch/x86/mm/fault.c
View File

@ -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;
}