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Date: Mon, 27 Feb 2012 10:23:46 -0600
From: Will Drewry <wad@...omium.org>
To: Kees Cook <kees@...ntu.com>
Cc: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
linux-doc@...r.kernel.org, kernel-hardening@...ts.openwall.com,
netdev@...r.kernel.org, x86@...nel.org, arnd@...db.de, davem@...emloft.net,
hpa@...or.com, mingo@...hat.com, oleg@...hat.com, peterz@...radead.org,
rdunlap@...otime.net, mcgrathr@...omium.org, tglx@...utronix.de, luto@....edu,
eparis@...hat.com, serge.hallyn@...onical.com, djm@...drot.org,
scarybeasts@...il.com, indan@....nu, pmoore@...hat.com,
akpm@...ux-foundation.org, corbet@....net, eric.dumazet@...il.com,
markus@...omium.org, coreyb@...ux.vnet.ibm.com, keescook@...omium.org
Subject: Re: [PATCH v11 06/12] seccomp: add system call filtering using BPF
On Sun, Feb 26, 2012 at 2:28 PM, Kees Cook <kees@...ntu.com> wrote:
> On Fri, Feb 24, 2012 at 09:21:45PM -0600, Will Drewry wrote:
>> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
>> index e8d76c5..25e8296 100644
>> --- a/kernel/seccomp.c
>> +++ b/kernel/seccomp.c
>> [...]
>> +static void seccomp_filter_log_failure(int syscall)
>> +{
>> + int compat = 0;
>> +#ifdef CONFIG_COMPAT
>> + compat = is_compat_task();
>> +#endif
>> + pr_info("%s[%d]: %ssystem call %d blocked at 0x%lx\n",
>> + current->comm, task_pid_nr(current),
>> + (compat ? "compat " : ""),
>> + syscall, KSTK_EIP(current));
>> +}
>> [...]
>> +#ifdef CONFIG_SECCOMP_FILTER
>> + case SECCOMP_MODE_FILTER:
>> + if (seccomp_run_filters(this_syscall) == SECCOMP_RET_ALLOW)
>> + return;
>> + seccomp_filter_log_failure(this_syscall);
>> + exit_code = SIGSYS;
>> + break;
>> +#endif
>> default:
>> BUG();
>> }
>> @@ -56,7 +324,7 @@ void __secure_computing(int this_syscall)
>> dump_stack();
>> #endif
>> audit_seccomp(this_syscall);
>> - do_exit(SIGKILL);
>> + do_exit(exit_code);
>> }
>
> I think the seccomp_filter_log_failure() use is redundant with the
> audit_seccomp call. Here's a possible reorganization of the logging...
Cool - a comment below:
> From: Kees Cook <keescook@...omium.org>
> Date: Sun, 26 Feb 2012 11:56:12 -0800
> Subject: [PATCH] seccomp: improve audit logging details
>
> This consolidates the seccomp filter error logging path and adds more
> details to the audit log.
>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> include/linux/audit.h | 8 ++++----
> kernel/auditsc.c | 9 +++++++--
> kernel/seccomp.c | 15 +--------------
> 3 files changed, 12 insertions(+), 20 deletions(-)
>
> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 9ff7a2c..5aa6cfc 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -463,7 +463,7 @@ extern void audit_putname(const char *name);
> extern void __audit_inode(const char *name, const struct dentry *dentry);
> extern void __audit_inode_child(const struct dentry *dentry,
> const struct inode *parent);
> -extern void __audit_seccomp(unsigned long syscall);
> +extern void __audit_seccomp(unsigned long syscall, long signr);
> extern void __audit_ptrace(struct task_struct *t);
>
> static inline int audit_dummy_context(void)
> @@ -508,10 +508,10 @@ static inline void audit_inode_child(const struct dentry *dentry,
> }
> void audit_core_dumps(long signr);
>
> -static inline void audit_seccomp(unsigned long syscall)
> +static inline void audit_seccomp(unsigned long syscall, long signr)
> {
> if (unlikely(!audit_dummy_context()))
> - __audit_seccomp(syscall);
> + __audit_seccomp(syscall, signr);
> }
>
> static inline void audit_ptrace(struct task_struct *t)
> @@ -634,7 +634,7 @@ extern int audit_signals;
> #define audit_inode(n,d) do { (void)(d); } while (0)
> #define audit_inode_child(i,p) do { ; } while (0)
> #define audit_core_dumps(i) do { ; } while (0)
> -#define audit_seccomp(i) do { ; } while (0)
> +#define audit_seccomp(i,s) do { ; } while (0)
> #define auditsc_get_stamp(c,t,s) (0)
> #define audit_get_loginuid(t) (-1)
> #define audit_get_sessionid(t) (-1)
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index af1de0f..74652fe 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -67,6 +67,7 @@
> #include <linux/syscalls.h>
> #include <linux/capability.h>
> #include <linux/fs_struct.h>
> +#include <linux/compat.h>
>
> #include "audit.h"
>
> @@ -2710,13 +2711,17 @@ void audit_core_dumps(long signr)
> audit_log_end(ab);
> }
>
> -void __audit_seccomp(unsigned long syscall)
> +void __audit_seccomp(unsigned long syscall, long signr)
> {
> struct audit_buffer *ab;
>
> ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_ANOM_ABEND);
> - audit_log_abend(ab, "seccomp", SIGKILL);
> + audit_log_abend(ab, "seccomp", signr);
> audit_log_format(ab, " syscall=%ld", syscall);
> +#ifdef CONFIG_COMPAT
> + audit_log_format(ab, " compat=%d", is_compat_task());
> +#endif
Should this just use syscall_get_arch to get the AUDIT_ARCH now? :)
> + audit_log_format(ab, " ip=0x%lx", KSTK_EIP(current));
> audit_log_end(ab);
> }
>
> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
> index 5aabc3c..40af83f 100644
> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -57,18 +57,6 @@ struct seccomp_filter {
> struct sock_filter insns[];
> };
>
> -static void seccomp_filter_log_failure(int syscall)
> -{
> - int compat = 0;
> -#ifdef CONFIG_COMPAT
> - compat = is_compat_task();
> -#endif
> - pr_info("%s[%d]: %ssystem call %d blocked at 0x%lx\n",
> - current->comm, task_pid_nr(current),
> - (compat ? "compat " : ""),
> - syscall, KSTK_EIP(current));
> -}
> -
> /**
> * get_u32 - returns a u32 offset into data
> * @data: a unsigned 64 bit value
> @@ -378,7 +366,6 @@ int __secure_computing_int(int this_syscall)
> default:
> break;
> }
> - seccomp_filter_log_failure(this_syscall);
> exit_code = SIGSYS;
> break;
> }
> @@ -390,7 +377,7 @@ int __secure_computing_int(int this_syscall)
> #ifdef SECCOMP_DEBUG
> dump_stack();
> #endif
> - audit_seccomp(this_syscall);
> + audit_seccomp(this_syscall, exit_code);
> do_exit(exit_code);
> return -1; /* never reached */
> }
> --
> 1.7.0.4
I'll pull this into the series if that's okay with you?
Thanks!
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