Patch "x86/mm/pkeys: Fix fill_sig_info_pkey" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

x86/mm/pkeys: Fix fill_sig_info_pkey

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-mm-pkeys-fix-fill_sig_info_pkey.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Eric W. Biederman" <[email protected]>
Date: Fri, 12 Jan 2018 14:31:35 -0600
Subject: x86/mm/pkeys: Fix fill_sig_info_pkey

From: Eric W. Biederman <[email protected]>

commit beacd6f7ed5e2915959442245b3b2480c2e37490 upstream.

SEGV_PKUERR is a signal specific si_code which happens to have the same numeric value as several others: BUS_MCEERR_AR, ILL_ILLTRP, FPE_FLTOVF, TRAP_HWBKPT, CLD_TRAPPED, POLL_ERR, SEGV_THREAD_ID, as such it is not safe to just test the si_code the signal number must also be tested to prevent a false positive in fill_sig_info_pkey.

This error was by inspection, and BUS_MCEERR_AR appears to be a real candidate for confusion. So pass in si_signo and check for SIG_SEGV to verify that it is actually a SEGV_PKUERR

---
 arch/x86/mm/fault.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

@@ -191,14 +191,15 @@ is_prefetch(struct pt_regs *regs, unsign
  * 6. T1   : reaches here, sees vma_pkey(vma)=5, when we really
  *	     faulted on a pte with its pkey=4.
  */
-static void fill_sig_info_pkey(int si_code, siginfo_t *info, u32 *pkey)
+static void fill_sig_info_pkey(int si_signo, int si_code, siginfo_t *info,
+		u32 *pkey)
 {
 	/* This is effectively an #ifdef */
 	if (!boot_cpu_has(X86_FEATURE_OSPKE))
 		return;
 
 	/* Fault not from Protection Keys: nothing to do */
-	if (si_code != SEGV_PKUERR)
+	if ((si_code != SEGV_PKUERR) || (si_signo != SIGSEGV))
 		return;
 	/*
 	 * force_sig_info_fault() is called from a number of

@@ -237,7 +238,7 @@ force_sig_info_fault(int si_signo, int s
 		lsb = PAGE_SHIFT;
 	info.si_addr_lsb = lsb;
 
-	fill_sig_info_pkey(si_code, &info, pkey);
+	fill_sig_info_pkey(si_signo, si_code, &info, pkey);
 
 	force_sig_info(si_signo, &info, tsk);
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/x86-mm-pkeys-fix-fill_sig_info_pkey.patch