BACKPORT: printk: hash addresses printed with %p
Currently there exist approximately 14 000 places in the kernel where
addresses are being printed using an unadorned %p. This potentially
leaks sensitive information regarding the Kernel layout in memory. Many
of these calls are stale, instead of fixing every call lets hash the
address by default before printing. This will of course break some
users, forcing code printing needed addresses to be updated.
Code that _really_ needs the address will soon be able to use the new
printk specifier %px to print the address.
For what it's worth, usage of unadorned %p can be broken down as
follows (thanks to Joe Perches).
$ git grep -E '%p[^A-Za-z0-9]' | cut -f1 -d"/" | sort | uniq -c
1084 arch
20 block
10 crypto
32 Documentation
8121 drivers
1221 fs
143 include
101 kernel
69 lib
100 mm
1510 net
40 samples
7 scripts
11 security
166 sound
152 tools
2 virt
Add function ptr_to_id() to map an address to a 32 bit unique
identifier. Hash any unadorned usage of specifier %p and any malformed
specifiers.
Signed-off-by: Tobin C. Harding <me@tobin.cc>
(cherry picked from commit ad67b74d2469d9b82aaa572d76474c95bc484d57)
Signed-off-by: Sandeep Patil <sspatil@android.com>
Bug: 78533979
Test: Build and boot cuttlefish
Test: Runtime tests by enabling CONFIG_TEST_PRINTF
Change-Id: I4a12d890d7b22caa502280d78cb4f6a09c866471
diff --git a/lib/test_printf.c b/lib/test_printf.c
index 563f10e..71ebfa4 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -24,24 +24,6 @@
#define PAD_SIZE 16
#define FILL_CHAR '$'
-#define PTR1 ((void*)0x01234567)
-#define PTR2 ((void*)(long)(int)0xfedcba98)
-
-#if BITS_PER_LONG == 64
-#define PTR1_ZEROES "000000000"
-#define PTR1_SPACES " "
-#define PTR1_STR "1234567"
-#define PTR2_STR "fffffffffedcba98"
-#define PTR_WIDTH 16
-#else
-#define PTR1_ZEROES "0"
-#define PTR1_SPACES " "
-#define PTR1_STR "1234567"
-#define PTR2_STR "fedcba98"
-#define PTR_WIDTH 8
-#endif
-#define PTR_WIDTH_STR stringify(PTR_WIDTH)
-
static unsigned total_tests __initdata;
static unsigned failed_tests __initdata;
static char *test_buffer __initdata;
@@ -217,30 +199,79 @@
test("a | | ", "%-3.s|%-3.0s|%-3.*s", "a", "b", 0, "c");
}
+#define PLAIN_BUF_SIZE 64 /* leave some space so we don't oops */
+
+#if BITS_PER_LONG == 64
+
+#define PTR_WIDTH 16
+#define PTR ((void *)0xffff0123456789ab)
+#define PTR_STR "ffff0123456789ab"
+#define ZEROS "00000000" /* hex 32 zero bits */
+
+static int __init
+plain_format(void)
+{
+ char buf[PLAIN_BUF_SIZE];
+ int nchars;
+
+ nchars = snprintf(buf, PLAIN_BUF_SIZE, "%p", PTR);
+
+ if (nchars != PTR_WIDTH || strncmp(buf, ZEROS, strlen(ZEROS)) != 0)
+ return -1;
+
+ return 0;
+}
+
+#else
+
+#define PTR_WIDTH 8
+#define PTR ((void *)0x456789ab)
+#define PTR_STR "456789ab"
+
+static int __init
+plain_format(void)
+{
+ /* Format is implicitly tested for 32 bit machines by plain_hash() */
+ return 0;
+}
+
+#endif /* BITS_PER_LONG == 64 */
+
+static int __init
+plain_hash(void)
+{
+ char buf[PLAIN_BUF_SIZE];
+ int nchars;
+
+ nchars = snprintf(buf, PLAIN_BUF_SIZE, "%p", PTR);
+
+ if (nchars != PTR_WIDTH || strncmp(buf, PTR_STR, PTR_WIDTH) == 0)
+ return -1;
+
+ return 0;
+}
+
+/*
+ * We can't use test() to test %p because we don't know what output to expect
+ * after an address is hashed.
+ */
static void __init
plain(void)
{
- test(PTR1_ZEROES PTR1_STR " " PTR2_STR, "%p %p", PTR1, PTR2);
- /*
- * The field width is overloaded for some %p extensions to
- * pass another piece of information. For plain pointers, the
- * behaviour is slightly odd: One cannot pass either the 0
- * flag nor a precision to %p without gcc complaining, and if
- * one explicitly gives a field width, the number is no longer
- * zero-padded.
- */
- test("|" PTR1_STR PTR1_SPACES " | " PTR1_SPACES PTR1_STR "|",
- "|%-*p|%*p|", PTR_WIDTH+2, PTR1, PTR_WIDTH+2, PTR1);
- test("|" PTR2_STR " | " PTR2_STR "|",
- "|%-*p|%*p|", PTR_WIDTH+2, PTR2, PTR_WIDTH+2, PTR2);
+ int err;
- /*
- * Unrecognized %p extensions are treated as plain %p, but the
- * alphanumeric suffix is ignored (that is, does not occur in
- * the output.)
- */
- test("|"PTR1_ZEROES PTR1_STR"|", "|%p0y|", PTR1);
- test("|"PTR2_STR"|", "|%p0y|", PTR2);
+ err = plain_hash();
+ if (err) {
+ pr_warn("plain 'p' does not appear to be hashed\n");
+ failed_tests++;
+ return;
+ }
+
+ err = plain_format();
+ if (err) {
+ pr_warn("hashing plain 'p' has unexpected format\n");
+ failed_tests++;
+ }
}
static void __init
@@ -251,6 +282,7 @@
static void __init
kernel_ptr(void)
{
+ /* We can't test this without access to kptr_restrict. */
}
static void __init