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security_syslog() should be called once only

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The final version of commit 637241a900 ("kmsg: honor dmesg_restrict
sysctl on /dev/kmsg") lost few hooks, as result security_syslog() are
processed incorrectly:

- open of /dev/kmsg checks syslog access permissions by using
  check_syslog_permissions() where security_syslog() is not called if
  dmesg_restrict is set.

- syslog syscall and /proc/kmsg calls do_syslog() where security_syslog
  can be executed twice (inside check_syslog_permissions() and then
  directly in do_syslog())

With this patch security_syslog() is called once only in all
syslog-related operations regardless of dmesg_restrict value.

Fixes: 637241a900 ("kmsg: honor dmesg_restrict sysctl on /dev/kmsg")
Signed-off-by: Vasily Averin <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Josh Boyer <[email protected]>
Cc: Eric Paris <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Vasily Averin 2015-06-25 15:01:44 -07:00 • committed by Linus Torvalds
commit d194e5d666
1 changed files with 4 additions and 7 deletions
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11
kernel/printk/printk.c
View file

@ -496,11 +496,11 @@ int check_syslog_permissions(int type, bool from_file)
* already done the capabilities checks at open time.
*/
if (from_file && type != SYSLOG_ACTION_OPEN)
return 0;
goto ok;
if (syslog_action_restricted(type)) {
if (capable(CAP_SYSLOG))
return 0;
goto ok;
/*
* For historical reasons, accept CAP_SYS_ADMIN too, with
* a warning.
@ -510,10 +510,11 @@ int check_syslog_permissions(int type, bool from_file)
"CAP_SYS_ADMIN but no CAP_SYSLOG "
"(deprecated).\n",
current->comm, task_pid_nr(current));
return 0;
goto ok;
}
return -EPERM;
}
ok:
return security_syslog(type);
}
@ -1299,10 +1300,6 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
if (error)
goto out;
error = security_syslog(type);
if (error)
return error;
switch (type) {
case SYSLOG_ACTION_CLOSE: /* Close log */
break;