Messages in this thread Patch in this message | | | From | Sergey Vlasov <> | Subject | [RFC PATCH 1/2] sys_syslog: check open permission for reading and getting unread count | Date | Wed, 8 Nov 2006 15:45:44 +0300 |
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The "read" (2) and "get unread count" (9) operations of sys_syslog() may also be invoked through /proc/kmsg; however, /proc/kmsg also performs security checks during open. Perform the same security check when these operations are invoked through the syslog system call.
Currently this does not change the behavior - for cap_syslog() and dummy_syslog() the "read" and "get unread count" operations are identical to "open", and selinux_syslog() maps all of them to SYSTEM__SYSLOG_MOD. The next patch will enable syslog read for normal users, so that a process could open /proc/kmsg, then drop privileges and continue reading kernel messages from the open file descriptor - then the added check in sys_syslog() will catch attempts to read kernel messages without having /proc/kmsg open.
Signed-off-by: Sergey Vlasov <vsu@altlinux.ru> --- kernel/printk.c | 16 +++++++++++++++- 1 files changed, 15 insertions(+), 1 deletions(-)
diff --git a/kernel/printk.c b/kernel/printk.c index 1149365..91c3f39 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -316,7 +316,21 @@ out: asmlinkage long sys_syslog(int type, char __user *buf, int len) { - return do_syslog(type, buf, len); + int retval; + + if ((type == 2) || (type == 9)) { + /* + * These operation can also be invoked through /proc/kmsg, but + * you need to have an open file descriptor for that. Make the + * syslog system call also require the syslog open permission. + */ + retval = security_syslog(1); + if (retval) + goto out; + } + retval = do_syslog(type, buf, len); +out: + return retval; } /* -- 1.4.3.3.gddcc6 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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