svn commit: r340995 - in head/sys: arm/arm arm64/arm64 riscv/riscv

[Eric van Gyzen]

Author: vangyzen
Date: Mon Nov 26 20:52:53 2018
New Revision: 340995
URL: https://svnweb.freebsd.org/changeset/base/340995

Log:
  Prevent kernel stack disclosure in signal delivery
  
  On arm64 and riscv platforms, sendsig() failed to zero the signal
  frame before copying it out to userspace.  Zero it.
  
  On arm, I believe all the contents of the frame were initialized,
  so there was no disclosure.  However, explicitly zero the whole frame
  because that fact could inadvertently change in the future,
  it's more clear to the reader, and I could be wrong in the first place.
  
  MFC after:	2 days
  Security:	similar to FreeBSD-EN-18:12.mem and CVE-2018-17155
  Sponsored by:	Dell EMC Isilon

Modified:
  head/sys/arm/arm/machdep.c
  head/sys/arm64/arm64/machdep.c
  head/sys/riscv/riscv/machdep.c

Modified: head/sys/arm/arm/machdep.c
==============================================================================
--- head/sys/arm/arm/machdep.c	Mon Nov 26 20:50:55 2018	(r340994)
+++ head/sys/arm/arm/machdep.c	Mon Nov 26 20:52:53 2018	(r340995)
@@ -641,6 +641,7 @@ sendsig(catcher, ksi, mask)
 	/* make the stack aligned */
 	fp = (struct sigframe *)STACKALIGN(fp);
 	/* Populate the siginfo frame. */
+	bzero(&frame, sizeof(frame));
 	get_mcontext(td, &frame.sf_uc.uc_mcontext, 0);
 #ifdef VFP
 	get_vfpcontext(td, &frame.sf_vfp);

Modified: head/sys/arm64/arm64/machdep.c
==============================================================================
--- head/sys/arm64/arm64/machdep.c	Mon Nov 26 20:50:55 2018	(r340994)
+++ head/sys/arm64/arm64/machdep.c	Mon Nov 26 20:52:53 2018	(r340995)
@@ -656,6 +656,7 @@ sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask
 	fp = (struct sigframe *)STACKALIGN(fp);
 
 	/* Fill in the frame to copy out */
+	bzero(&frame, sizeof(frame));
 	get_mcontext(td, &frame.sf_uc.uc_mcontext, 0);
 	get_fpcontext(td, &frame.sf_uc.uc_mcontext);
 	frame.sf_si = ksi->ksi_info;

Modified: head/sys/riscv/riscv/machdep.c
==============================================================================
--- head/sys/riscv/riscv/machdep.c	Mon Nov 26 20:50:55 2018	(r340994)
+++ head/sys/riscv/riscv/machdep.c	Mon Nov 26 20:52:53 2018	(r340995)
@@ -582,6 +582,7 @@ sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask
 	fp = (struct sigframe *)STACKALIGN(fp);
 
 	/* Fill in the frame to copy out */
+	bzero(&frame, sizeof(frame));
 	get_mcontext(td, &frame.sf_uc.uc_mcontext, 0);
 	get_fpcontext(td, &frame.sf_uc.uc_mcontext);
 	frame.sf_si = ksi->ksi_info;