support single arguments that are large, not just large lists of execve args.
This also means we never have to get a kernel buffer larger than
MAX_EXECVE_AUDIT_LEN no matter how large the argument is. Before this patch
we could need to allocate 32 consecutive pages to hold one argument which could
pretty easily oom.

a single argument larger than MAX_EXECVE_AUDIT_LEN is broken into multiple
records and have a format like a10[0] a10[1] a10[2] etc.

Signed-off-by: Eric Paris
---

example audit log (about 50k long) for the whole patch series can be
found at http://people.redhat.com/~eparis/audit/audit.log the execve in
question was something like:

program_name [about 50 arguments] [one argument which is about 17k long] [about 1000 arguments]

kernel/auditsc.c | 42 +++++++++++++++++++++++++++++++++++++++++
1 files changed, 42 insertions(+), 0 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 4176db6..ffc8d4b 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -853,6 +853,48 @@ static void audit_log_execve_info(struct audit_context *context,
send_sig(SIGKILL, current, 0);
}

+ if (unlikely(len > MAX_EXECVE_AUDIT_LEN)) {
+ /* deal with single arugments > MAX_EXECVE_AUDIT_LEN */
+ int j;
+ const long tmplen = sizeof(char) * MAX_EXECVE_AUDIT_LEN;
+
+ buf = kmalloc(tmplen + 1, GFP_KERNEL);
+ if (!buf) {
+ audit_panic("out of memory for argv string\n");
+ return;
+ }
+ buf[tmplen] = '\0';
+ for (j = 0; len > 0; j++) {
+ if (len > tmplen) {
+ ret = copy_from_user(buf, p, tmplen);
+ p += tmplen;
+ len -= tmplen;
+ } else {
+ ret = copy_from_user(buf, p, len);
+ /* p is at the next arg */
+ p += len;
+ /* 27 is the max length of a%d[%d] */
+ len_sent = len + 27;
+ len = 0;
+ }
+ if (ret) {
+ WARN_ON(1);
+ send_sig(SIGKILL, current, 0);
+ }
+ audit_log_end(*ab);
+ *ab = audit_log_start(context, GFP_KERNEL,
+ AUDIT_EXECVE);
+ if (!*ab) {
+ kfree(buf);
+ return;
+ }
+ audit_log_format(*ab, "a%d[%d]=", i, j);
+ audit_log_untrustedstring(*ab, buf);
+ audit_log_format(*ab, "\n");
+ }
+ continue;
+ }
+
buf = kmalloc(len, GFP_KERNEL);
if (!buf) {
audit_panic("out of memory for argv string\n");


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