X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2Fvsprintf.c;h=48586ac3a62e3691c4950c1c72d904e6ebf036af;hb=3aeb58ab6216d864821e8dafb248e8d77403f3e9;hp=26559bdb4c49737a2d0e33006476f6a9be94385f;hpb=1ef68ec462571955f2a667ddf1ffe279848709d7;p=firefly-linux-kernel-4.4.55.git

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 26559bdb4c49..48586ac3a62e 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -27,6 +27,7 @@
 #include <linux/uaccess.h>
 #include <linux/ioport.h>
 #include <linux/dcache.h>
+#include <linux/cred.h>
 #include <net/addrconf.h>
 
 #include <asm/page.h>		/* for PAGE_SIZE */
@@ -1218,6 +1219,8 @@ int kptr_restrict __read_mostly;
  *            The maximum supported length is 64 bytes of the input. Consider
  *            to use print_hex_dump() for the larger input.
  * - 'a' For a phys_addr_t type and its derivative types (passed by reference)
+ * - 'd[234]' For a dentry name (optionally 2-4 last components)
+ * - 'D[234]' Same as 'd' but for a struct file
  *
  * Note: The difference between 'S' and 'F' is that on ia64 and ppc64
  * function pointers are really function descriptors, which contain a
@@ -1312,11 +1315,37 @@ 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':