tracing: Check for no filter when processing event filters (CVE-2018-12714)

debian/changelog

@@ -85,6 +85,7 @@ linux (4.17.3-1) UNRELEASED; urgency=medium
   * aufs: Update support patchset to aufs4.x-rcN-20180611
   * debian/rules.d/scripts/mod/gendef.py: Use Python 3
   * debian/rules: Fix pkg.linux.notools build profile
+  * tracing: Check for no filter when processing event filters (CVE-2018-12714)
 
   [ Romain Perier ]
   * [x86] amdgpu: Enable DCN 1.0 Raven family (Closes: #901349)

debian/patches/bugfix/all/tracing-check-for-no-filter-when-processing-event-fi.patch

@@ -0,0 +1,61 @@
+From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
+Date: Thu, 21 Jun 2018 13:20:53 -0400
+Subject: tracing: Check for no filter when processing event filters
+Origin: https://git.kernel.org/linus/70303420b5721c38998cf987e6b7d30cc62d4ff1
+Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2018-12714
+
+The syzkaller detected a out-of-bounds issue with the events filter code,
+specifically here:
+
+	prog[N].pred = NULL;					/* #13 */
+	prog[N].target = 1;		/* TRUE */
+	prog[N+1].pred = NULL;
+	prog[N+1].target = 0;		/* FALSE */
+->	prog[N-1].target = N;
+	prog[N-1].when_to_branch = false;
+
+As that's the first reference to a "N-1" index, it appears that the code got
+here with N = 0, which means the filter parser found no filter to parse
+(which shouldn't ever happen, but apparently it did).
+
+Add a new error to the parsing code that will check to make sure that N is
+not zero before going into this part of the code. If N = 0, then -EINVAL is
+returned, and a error message is added to the filter.
+
+Cc: stable@vger.kernel.org
+Fixes: 80765597bc587 ("tracing: Rewrite filter logic to be simpler and faster")
+Reported-by: air icy <icytxw@gmail.com>
+bugzilla url: https://bugzilla.kernel.org/show_bug.cgi?id=200019
+Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
+---
+ kernel/trace/trace_events_filter.c | 10 +++++++++-
+ 1 file changed, 9 insertions(+), 1 deletion(-)
+
+diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
+index e1c818dbc0d7..0dceb77d1d42 100644
+--- a/kernel/trace/trace_events_filter.c
++++ b/kernel/trace/trace_events_filter.c
+@@ -78,7 +78,8 @@ static const char * ops[] = { OPS };
+ 	C(TOO_MANY_PREDS,	"Too many terms in predicate expression"), \
+ 	C(INVALID_FILTER,	"Meaningless filter expression"),	\
+ 	C(IP_FIELD_ONLY,	"Only 'ip' field is supported for function trace"), \
+-	C(INVALID_VALUE,	"Invalid value (did you forget quotes)?"),
++	C(INVALID_VALUE,	"Invalid value (did you forget quotes)?"), \
++	C(NO_FILTER,		"No filter found"),
+ 
+ #undef C
+ #define C(a, b)		FILT_ERR_##a
+@@ -550,6 +551,13 @@ predicate_parse(const char *str, int nr_parens, int nr_preds,
+ 		goto out_free;
+ 	}
+ 
++	if (!N) {
++		/* No program? */
++		ret = -EINVAL;
++		parse_error(pe, FILT_ERR_NO_FILTER, ptr - str);
++		goto out_free;
++	}
++
+ 	prog[N].pred = NULL;					/* #13 */
+ 	prog[N].target = 1;		/* TRUE */
+ 	prog[N+1].pred = NULL;

debian/patches/series

@@ -134,6 +134,7 @@ debian/i386-686-pae-pci-set-pci-nobios-by-default.patch
 bugfix/x86/virt-vbox-Only-copy_from_user-the-request-header-onc.patch
 
 # Fix exported symbol versions
+bugfix/all/tracing-check-for-no-filter-when-processing-event-fi.patch
 bugfix/all/module-disable-matching-missing-version-crc.patch
 
 # Tools bug fixes