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SubjectRe: [PATCH v11 06/12] seccomp: add system call filtering using BPF
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...

From: Kees Cook <keescook@chromium.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@chromium.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
+ 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

--
Kees Cook


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