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cap_syslog: accept CAP_SYS_ADMIN for now 

In commit ce6ada35bd ("security: Define CAP_SYSLOG") Serge Hallyn
introduced CAP_SYSLOG, but broke backwards compatibility by no longer
accepting CAP_SYS_ADMIN as an override (it would cause a warning and
then reject the operation).

Re-instate CAP_SYS_ADMIN - but keeping the warning - as an acceptable
capability until any legacy applications have been updated.  There are
apparently applications out there that drop all capabilities except for
CAP_SYS_ADMIN in order to access the syslog.

(This is a re-implementation of a patch by Serge, cleaning the logic up
and making the code more readable)

Acked-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: James Morris <jmorris@namei.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2011-02-10 17:53:55 -08:00
parent 67d019528e
commit ee24aebffb
1 changed files with 35 additions and 19 deletions
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54
kernel/printk.c
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@ -262,25 +262,47 @@ int dmesg_restrict = 1;
int dmesg_restrict;
#endif
static int syslog_action_restricted(int type)
{
if (dmesg_restrict)
return 1;
/* Unless restricted, we allow "read all" and "get buffer size" for everybody */
return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
}
static int check_syslog_permissions(int type, bool from_file)
{
/*
* If this is from /proc/kmsg and we've already opened it, then we've
* already done the capabilities checks at open time.
*/
if (from_file && type != SYSLOG_ACTION_OPEN)
return 0;
if (syslog_action_restricted(type)) {
if (capable(CAP_SYSLOG))
return 0;
/* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
if (capable(CAP_SYS_ADMIN)) {
WARN_ONCE(1, "Attempt to access syslog with CAP_SYS_ADMIN "
"but no CAP_SYSLOG (deprecated).\n");
return 0;
}
return -EPERM;
}
return 0;
}
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;
int error;
/*
* If this is from /proc/kmsg we only do the capabilities checks
* at open time.
*/
if (type == SYSLOG_ACTION_OPEN || !from_file) {
if (dmesg_restrict && !capable(CAP_SYSLOG))
goto warn; /* switch to return -EPERM after 2.6.39 */
if ((type != SYSLOG_ACTION_READ_ALL &&
type != SYSLOG_ACTION_SIZE_BUFFER) &&
!capable(CAP_SYSLOG))
goto warn; /* switch to return -EPERM after 2.6.39 */
}
error = check_syslog_permissions(type, from_file);
if (error)
goto out;
error = security_syslog(type);
if (error)
@ -423,12 +445,6 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
}
out:
return error;
warn:
/* remove after 2.6.39 */
if (capable(CAP_SYS_ADMIN))
WARN_ONCE(1, "Attempt to access syslog with CAP_SYS_ADMIN "
"but no CAP_SYSLOG (deprecated and denied).\n");
return -EPERM;
}
SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)