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syslog: check cap_syslog when dmesg_restrict

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Eric Paris pointed out that it doesn't make sense to require
both CAP_SYS_ADMIN and CAP_SYSLOG for certain syslog actions.
So require CAP_SYSLOG, not CAP_SYS_ADMIN, when dmesg_restrict
is set.

(I'm also consolidating the now common error path)

Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: Eric Paris <eparis@redhat.com>
Acked-by: Kees Cook <kees.cook@canonical.com>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
Serge E. Hallyn 2010-12-08 15:19:01 +00:00 committed by James Morris
parent 5c6d1125f8
commit 38ef4c2e43
2 changed files with 11 additions and 11 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

2
Documentation/sysctl/kernel.txt
View file

@ -219,7 +219,7 @@ dmesg_restrict:
This toggle indicates whether unprivileged users are prevented from using
dmesg(8) to view messages from the kernel's log buffer. When
dmesg_restrict is set to (0) there are no restrictions. When
dmesg_restrict is set set to (1), users must have CAP_SYS_ADMIN to use
dmesg_restrict is set set to (1), users must have CAP_SYSLOG to use
dmesg(8).
The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the default

20
kernel/printk.c
View file

@ -279,18 +279,12 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
* at open time.
*/
if (type == SYSLOG_ACTION_OPEN || !from_file) {
if (dmesg_restrict && !capable(CAP_SYS_ADMIN))
return -EPERM;
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)) {
/* remove after 2.6.38 */
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;
}
!capable(CAP_SYSLOG))
goto warn; /* switch to return -EPERM after 2.6.39 */
}
error = security_syslog(type);
@ -434,6 +428,12 @@ 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)