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SubjectRe: Potential out-of-bounds in ftrace_regex_release
On Wed, 9 Oct 2013 14:05:26 +0400
Andrey Konovalov <andreyknvl@google.com> wrote:

> So I still think that the bug is in 'trage_get_user()':
> Checking that 'parser->idx < parser->size - 1' is not performed in 'if
> (isspace(ch))' section, so 'parser->idx' becomes equal to
> 'parser->size' after 'parser->buffer[parser->idx++] = ch;'.
> (However in 'while (cnt && !isspace(ch))' loop checking is performed.)

Yep, you are correct. I put in some printk's and did same writing to
the set_events file and was able to prove that I could get that "0"
written into the +1 overflow boundary.

Can you try this patch to see if it fixes it for you.

Thanks,

-- Steve

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d5f7c4d..063a92b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -843,9 +843,12 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
if (isspace(ch)) {
parser->buffer[parser->idx] = 0;
parser->cont = false;
- } else {
+ } else if (parser->idx < parser->size - 1) {
parser->cont = true;
parser->buffer[parser->idx++] = ch;
+ } else {
+ ret = -EINVAL;
+ goto out;
}

*ppos += read;


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