Commit bdf4c48a authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds

audit: rework execve audit

The purpose of audit_bprm() is to log the argv array to a userspace daemon at
the end of the execve system call.  Since user-space hasn't had time to run,
this array is still in pristine state on the process' stack; so no need to
copy it, we can just grab it from there.

In order to minimize the damage to audit_log_*() copy each string into a
temporary kernel buffer first.

Currently the audit code requires that the full argument vector fits in a
single packet.  So currently it does clip the argv size to a (sysctl) limit,
but only when execve auditing is enabled.

If the audit protocol gets extended to allow for multiple packets this check
can be removed.
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarOllie Wild <aaw@google.com>
Cc: <linux-audit@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b111757c
......@@ -1065,6 +1065,13 @@ check the amount of free space (value is in seconds). Default settings are: 4,
resume it if we have a value of 3 or more percent; consider information about
the amount of free space valid for 30 seconds
audit_argv_kb
-------------
The file contains a single value denoting the limit on the argv array size
for execve (in KiB). This limit is only applied when system call auditing for
execve is enabled, otherwise the value is ignored.
ctrl-alt-del
------------
......
......@@ -1154,6 +1154,7 @@ int do_execve(char * filename,
{
struct linux_binprm *bprm;
struct file *file;
unsigned long env_p;
int retval;
int i;
......@@ -1208,9 +1209,11 @@ int do_execve(char * filename,
if (retval < 0)
goto out;
env_p = bprm->p;
retval = copy_strings(bprm->argc, argv, bprm);
if (retval < 0)
goto out;
bprm->argv_len = env_p - bprm->p;
retval = search_binary_handler(bprm,regs);
if (retval >= 0) {
......
......@@ -40,6 +40,7 @@ struct linux_binprm{
unsigned interp_flags;
unsigned interp_data;
unsigned long loader, exec;
unsigned long argv_len;
};
#define BINPRM_FLAGS_ENFORCE_NONDUMP_BIT 0
......
......@@ -153,7 +153,7 @@ struct audit_aux_data_execve {
struct audit_aux_data d;
int argc;
int envc;
char mem[0];
struct mm_struct *mm;
};
struct audit_aux_data_socketcall {
......@@ -831,6 +831,55 @@ static int audit_log_pid_context(struct audit_context *context, pid_t pid,
return rc;
}
static void audit_log_execve_info(struct audit_buffer *ab,
struct audit_aux_data_execve *axi)
{
int i;
long len, ret;
const char __user *p = (const char __user *)axi->mm->arg_start;
char *buf;
if (axi->mm != current->mm)
return; /* execve failed, no additional info */
for (i = 0; i < axi->argc; i++, p += len) {
len = strnlen_user(p, MAX_ARG_PAGES*PAGE_SIZE);
/*
* We just created this mm, if we can't find the strings
* we just copied into it something is _very_ wrong. Similar
* for strings that are too long, we should not have created
* any.
*/
if (!len || len > MAX_ARG_STRLEN) {
WARN_ON(1);
send_sig(SIGKILL, current, 0);
}
buf = kmalloc(len, GFP_KERNEL);
if (!buf) {
audit_panic("out of memory for argv string\n");
break;
}
ret = copy_from_user(buf, p, len);
/*
* There is no reason for this copy to be short. We just
* copied them here, and the mm hasn't been exposed to user-
* space yet.
*/
if (!ret) {
WARN_ON(1);
send_sig(SIGKILL, current, 0);
}
audit_log_format(ab, "a%d=", i);
audit_log_untrustedstring(ab, buf);
audit_log_format(ab, "\n");
kfree(buf);
}
}
static void audit_log_exit(struct audit_context *context, struct task_struct *tsk)
{
int i, call_panic = 0;
......@@ -971,13 +1020,7 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
case AUDIT_EXECVE: {
struct audit_aux_data_execve *axi = (void *)aux;
int i;
const char *p;
for (i = 0, p = axi->mem; i < axi->argc; i++) {
audit_log_format(ab, "a%d=", i);
p = audit_log_untrustedstring(ab, p);
audit_log_format(ab, "\n");
}
audit_log_execve_info(ab, axi);
break; }
case AUDIT_SOCKETCALL: {
......@@ -1821,32 +1864,31 @@ int __audit_ipc_set_perm(unsigned long qbytes, uid_t uid, gid_t gid, mode_t mode
return 0;
}
int audit_argv_kb = 32;
int audit_bprm(struct linux_binprm *bprm)
{
struct audit_aux_data_execve *ax;
struct audit_context *context = current->audit_context;
unsigned long p, next;
void *to;
if (likely(!audit_enabled || !context || context->dummy))
return 0;
ax = kmalloc(sizeof(*ax) + PAGE_SIZE * MAX_ARG_PAGES - bprm->p,
GFP_KERNEL);
/*
* Even though the stack code doesn't limit the arg+env size any more,
* the audit code requires that _all_ arguments be logged in a single
* netlink skb. Hence cap it :-(
*/
if (bprm->argv_len > (audit_argv_kb << 10))
return -E2BIG;
ax = kmalloc(sizeof(*ax), GFP_KERNEL);
if (!ax)
return -ENOMEM;
ax->argc = bprm->argc;
ax->envc = bprm->envc;
for (p = bprm->p, to = ax->mem; p < MAX_ARG_PAGES*PAGE_SIZE; p = next) {
struct page *page = bprm->page[p / PAGE_SIZE];
void *kaddr = kmap(page);
next = (p + PAGE_SIZE) & ~(PAGE_SIZE - 1);
memcpy(to, kaddr + (p & (PAGE_SIZE - 1)), next - p);
to += next - p;
kunmap(page);
}
ax->mm = bprm->mm;
ax->d.type = AUDIT_EXECVE;
ax->d.next = context->aux;
context->aux = (void *)ax;
......
......@@ -78,6 +78,7 @@ extern int percpu_pagelist_fraction;
extern int compat_log;
extern int maps_protect;
extern int sysctl_stat_interval;
extern int audit_argv_kb;
/* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
static int maxolduid = 65535;
......@@ -306,6 +307,16 @@ static ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = &proc_dointvec,
},
#ifdef CONFIG_AUDITSYSCALL
{
.ctl_name = CTL_UNNUMBERED,
.procname = "audit_argv_kb",
.data = &audit_argv_kb,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
#endif
{
.ctl_name = KERN_CORE_PATTERN,
.procname = "core_pattern",
......
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