Printing kernel pointers via %pK has a minor defect when
kptr_restrict is set to 2: the pointer may be emitted
as "pK-error" instead of all 0's when in an interrupt.
Fix this defect, neaten the code, and correct the sysctl
documentation.
Add missing documentation for 2 other uses: %pNF and %pV.
Trivially reduces vsprintf.o object size:
$ size lib/vsprintf.o*
text data bss dec hex filename
14536 6 0 14542 38ce lib/vsprintf.o.new
14568 6 0 14574 38ee lib/vsprintf.o.old
Signed-off-by: Joe Perches <j...@perches.com>
---
Documentation/sysctl/kernel.txt | 17 +++++++++--------
lib/vsprintf.c | 38 ++++++++++++++++++++++++--------------
2 files changed, 33 insertions(+), 22 deletions(-)
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 9d4c1d1..c17d5ca 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -289,14 +289,15 @@ Default value is "/sbin/hotplug".
kptr_restrict:
-This toggle indicates whether restrictions are placed on
-exposing kernel addresses via /proc and other interfaces. When
-kptr_restrict is set to (0), there are no restrictions. When
-kptr_restrict is set to (1), the default, kernel pointers
-printed using the %pK format specifier will be replaced with 0's
-unless the user has CAP_SYSLOG. When kptr_restrict is set to
-(2), kernel pointers printed using %pK will be replaced with 0's
-regardless of privileges.
+This toggle indicates whether restrictions are placed on exposing kernel
+addresses via /proc and other interfaces.
+
+When kptr_restrict is set to (0), the default, there are no restrictions.
+When kptr_restrict is set to (1), kernel pointers printed using the %pK
+format specifier will be replaced with 0's unless the user has CAP_SYSLOG
+and effective user and group ids are equal to the real ids.
+When kptr_restrict is set to (2), kernel pointers printed using %pK will
+be replaced with 0's regardless of privileges.
==============================================================
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 26559bd..ce55f52 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1301,21 +1301,28 @@ char *pointer(const char *fmt, char *buf, char *end,
void *ptr,
va_end(va);
return buf;
}
- case 'K':
- /*
- * %pK cannot be used in IRQ context because its test
- * for CAP_SYSLOG would be meaningless.
- */
- if (kptr_restrict && (in_irq() || in_serving_softirq() ||
- in_nmi())) {
- if (spec.field_width == -1)
- 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))))
+ case 'K': /* see: Documentation/sysctl/kernel.txt */
+ switch (kptr_restrict) {
+ case 0: /* None (default) */
+ break;
+ case 1: /* Restricted */
+ if (in_irq() || in_serving_softirq() || in_nmi()) {
+ /*
+ * This cannot be used in IRQ context because
+ * the test for CAP_SYSLOG would be meaningless
+ */
+ if (spec.field_width == -1)
+ spec.field_width = default_width;
+ return string(buf, end, "pK-error", spec);
+ }
+ if (!has_capability_noaudit(current, CAP_SYSLOG))
+ ptr = NULL;
+ break;
+ case 2: /* Never - Always emit 0 */
+ default:
ptr = NULL;
+ break;
+ }
break;
case 'N':
switch (fmt[1]) {
@@ -1574,6 +1581,9 @@ qualifier:
* %piS depending on sa_family of 'struct sockaddr *' print IPv4/IPv6 address
* %pU[bBlL] print a UUID/GUID in big or little endian using lower or upper
* case.
+ * %pV recurse and output a struct va_format (const char *fmt, va_list *)
+ * %pK output a kernel address or 0 depending on sysctl kptr_restrict
+ * %NF output a netdev_features_t
* %*ph[CDN] a variable-length hex string with a separator (supports up to 64
* bytes of the input)
* %n is ignored
--
1.8.1.2.459.gbcd45b4.dirty
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