Re: [PATCH] Fix dmesg_restrict build failure withCONFIG_EMBEDDED=y and CONFIG_PRINTK=n

From: Joe Perches
Date: Sat Nov 13 2010 - 15:01:12 EST


Maybe something like this is better?

Remove dmesg_restrict from kernel.h printk.c
Move dmesg_restrict to security/commoncap.c
Add extern int dmesg_restrict to kernel/sysctl.c
Use CONFIG_SECURITY_DMESG_RESTRICT as variable guard

uncompiled/untested.

---
include/linux/kernel.h | 1 -
kernel/printk.c | 6 ------
kernel/sysctl.c | 6 ++++++
security/Kconfig | 1 +
security/commoncap.c | 8 ++++++++
5 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index fc3da9e..b526947 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -293,7 +293,6 @@ extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
unsigned int interval_msec);

extern int printk_delay_msec;
-extern int dmesg_restrict;

/*
* Print a one-time message (analogous to WARN_ONCE() et al):
diff --git a/kernel/printk.c b/kernel/printk.c
index 38e7d58..b2ebaee 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -261,12 +261,6 @@ static inline void boot_delay_msec(void)
}
#endif

-#ifdef CONFIG_SECURITY_DMESG_RESTRICT
-int dmesg_restrict = 1;
-#else
-int dmesg_restrict;
-#endif
-
int do_syslog(int type, char __user *buf, int len, bool from_file)
{
unsigned i, j, limit, count;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index b65bf63..f8ba761 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -106,6 +106,10 @@ extern int sysctl_nr_trim_pages;
#ifdef CONFIG_BLOCK
extern int blk_iopoll_enabled;
#endif
+#ifdef CONFIG_SECURITY_DMESG_RESTRICT
+extern int dmesg_restrict;
+#endif
+

/* Constants used for minimum and maximum */
#ifdef CONFIG_LOCKUP_DETECTOR
@@ -703,6 +707,7 @@ static struct ctl_table kern_table[] = {
.extra2 = &ten_thousand,
},
#endif
+#ifdef CONFIG_SECURITY_DMESG_RESTRICT
{
.procname = "dmesg_restrict",
.data = &dmesg_restrict,
@@ -712,6 +717,7 @@ static struct ctl_table kern_table[] = {
.extra1 = &zero,
.extra2 = &one,
},
+#endif
{
.procname = "ngroups_max",
.data = &ngroups_max,
diff --git a/security/Kconfig b/security/Kconfig
index e80da95..c6583d6 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -41,6 +41,7 @@ config KEYS_DEBUG_PROC_KEYS

config SECURITY_DMESG_RESTRICT
bool "Restrict unprivileged access to the kernel syslog"
+ depends on SECURITY
default n
help
This enforces restrictions on unprivileged users reading the kernel
diff --git a/security/commoncap.c b/security/commoncap.c
index 04b80f9..08066df 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -883,6 +883,12 @@ error:
return error;
}

+#ifdef CONFIG_SECURITY_DMESG_RESTRICT
+int dmesg_restrict = 1;
+#else
+int dmesg_restrict;
+#endif
+
/**
* cap_syslog - Determine whether syslog function is permitted
* @type: Function requested
@@ -895,8 +901,10 @@ int cap_syslog(int type, bool from_file)
{
if (type != SYSLOG_ACTION_OPEN && from_file)
return 0;
+#ifdef CONFIG_SECURITY_DMESG_RESTRICT
if (dmesg_restrict && !capable(CAP_SYS_ADMIN))
return -EPERM;
+#endif
if ((type != SYSLOG_ACTION_READ_ALL &&
type != SYSLOG_ACTION_SIZE_BUFFER) && !capable(CAP_SYS_ADMIN))
return -EPERM;


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