diff options
| author | Richard Weinberger <richard@nod.at> | 2011-03-23 16:43:11 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-03-23 19:46:54 -0700 |
| commit | bfdc0b497faa82a0ba2f9dddcf109231dd519fcc (patch) | |
| tree | 932897262447dacb7158b81209748a295d93e20b | |
| parent | cb16e95fa2996743a6e80a665ed2ed0590bd38cf (diff) | |
sysctl: restrict write access to dmesg_restrict
When dmesg_restrict is set to 1 CAP_SYS_ADMIN is needed to read the kernel
ring buffer. But a root user without CAP_SYS_ADMIN is able to reset
dmesg_restrict to 0.
This is an issue when e.g. LXC (Linux Containers) are used and complete
user space is running without CAP_SYS_ADMIN. A unprivileged and jailed
root user can bypass the dmesg_restrict protection.
With this patch writing to dmesg_restrict is only allowed when root has
CAP_SYS_ADMIN.
Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Dan Rosenberg <drosenberg@vsecurity.com>
Acked-by: Serge E. Hallyn <serge@hallyn.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Kees Cook <kees.cook@canonical.com>
Cc: James Morris <jmorris@namei.org>
Cc: Eugene Teo <eugeneteo@kernel.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | kernel/sysctl.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 97ab1690f5ed..c0bb32414b17 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -170,6 +170,11 @@ static int proc_taint(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos); #endif +#ifdef CONFIG_PRINTK +static int proc_dmesg_restrict(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos); +#endif + #ifdef CONFIG_MAGIC_SYSRQ /* Note: sysrq code uses it's own private copy */ static int __sysrq_enabled = SYSRQ_DEFAULT_ENABLE; @@ -707,7 +712,7 @@ static struct ctl_table kern_table[] = { .data = &kptr_restrict, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec_minmax, + .proc_handler = proc_dmesg_restrict, .extra1 = &zero, .extra2 = &two, }, @@ -2394,6 +2399,17 @@ static int proc_taint(struct ctl_table *table, int write, return err; } +#ifdef CONFIG_PRINTK +static int proc_dmesg_restrict(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + if (write && !capable(CAP_SYS_ADMIN)) + return -EPERM; + + return proc_dointvec_minmax(table, write, buffer, lenp, ppos); +} +#endif + struct do_proc_dointvec_minmax_conv_param { int *min; int *max; |