X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2Fvsprintf.c;h=620fae4c11f6f1d22ad5deab8f88843f1d957b1c;hb=088d7dadf9ce9e4923355f1e9ad02cd130dcfd7e;hp=e149c6416384a2a335783f0db538e030e90e6e69;hpb=007b703b3ed74e9af9c0576e7698ccda0170d370;p=firefly-linux-kernel-4.4.55.git

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index e149c6416384..620fae4c11f6 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -26,6 +26,7 @@
 #include <linux/math64.h>
 #include <linux/uaccess.h>
 #include <linux/ioport.h>
+#include <linux/cred.h>
 #include <net/addrconf.h>
 
 #include <asm/page.h>		/* for PAGE_SIZE */
@@ -1118,11 +1119,37 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 				spec.field_width = default_width;
 			return string(buf, end, "pK-error", spec);
 		}
-		if (!((kptr_restrict == 0) ||
-		      (kptr_restrict == 1 &&
-		       has_capability_noaudit(current, CAP_SYSLOG))))
+
+		switch (kptr_restrict) {
+		case 0:
+			/* Always print %pK values */
+			break;
+		case 1: {
+			/*
+			 * Only print the real pointer value if the current
+			 * process has CAP_SYSLOG and is running with the
+			 * same credentials it started with. This is because
+			 * access to files is checked at open() time, but %pK
+			 * checks permission at read() time. We don't want to
+			 * leak pointer values if a binary opens a file using
+			 * %pK and then elevates privileges before reading it.
+			 */
+			const struct cred *cred = current_cred();
+
+			if (!has_capability_noaudit(current, CAP_SYSLOG) ||
+			    !uid_eq(cred->euid, cred->uid) ||
+			    !gid_eq(cred->egid, cred->gid))
+				ptr = NULL;
+			break;
+		}
+		case 2:
+		default:
+			/* Always print 0's for %pK */
 			ptr = NULL;
+			break;
+		}
 		break;
+
 	case 'N':
 		switch (fmt[1]) {
 		case 'F':