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syslog: distinguish between /proc/kmsg and syscalls

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This allows the LSM to distinguish between syslog functions originating
from /proc/kmsg access and direct syscalls.  By default, the commoncaps
will now no longer require CAP_SYS_ADMIN to read an opened /proc/kmsg
file descriptor.  For example the kernel syslog reader can now drop
privileges after opening /proc/kmsg, instead of staying privileged with
CAP_SYS_ADMIN.  MAC systems that implement security_syslog have unchanged
behavior.

Signed-off-by: Kees Cook <kees.cook@canonical.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
Kees Cook
2010-02-03 15:36:43 -08:00
committed by James Morris
parent 0719aaf5ea
commit 002345925e
8 changed files with 59 additions and 22 deletions
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7
kernel/printk.c
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@@ -35,6 +35,7 @@
#include <linux/kexec.h>
#include <linux/ratelimit.h>
#include <linux/kmsg_dump.h>
#include <linux/syslog.h>
#include <asm/uaccess.h>
@@ -273,14 +274,14 @@ static inline void boot_delay_msec(void)
* 9 -- Return number of unread characters in the log buffer
* 10 -- Return size of the log buffer
*/
int do_syslog(int type, char __user *buf, int len)
int do_syslog(int type, char __user *buf, int len, bool from_file)
{
unsigned i, j, limit, count;
int do_clear = 0;
char c;
int error = 0;
error = security_syslog(type);
error = security_syslog(type, from_file);
if (error)
return error;
@@ -417,7 +418,7 @@ out:
SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
{
return do_syslog(type, buf, len);
return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
}
/*