* [PATCH] tracing: fix potential null pointer dereference on rctr_end
@ 2018-09-27 22:47 Colin King
2019-03-28 0:37 ` Steven Rostedt
0 siblings, 1 reply; 2+ messages in thread
From: Colin King @ 2018-09-27 22:47 UTC (permalink / raw)
To: Steven Rostedt, Ingo Molnar; +Cc: kernel-janitors, linux-kernel
From: Colin Ian King <colin.king@canonical.com>
Currently rctr_end may assigned null if strchr() fails leading to
a null pointer dereference in the following check on *(rctr_end + 1).
Fix this by also adding a null pointer check before the dereference.
Detected by CoverityScan, CID#1473700 ("Dereference null return value")
Fixes: 1cc33161a83d ("uprobes: Support SDT markers having reference count (semaphore)")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
kernel/trace/trace_uprobe.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 3a7c73c40007..c5514651e61f 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -477,7 +477,7 @@ static int create_trace_uprobe(int argc, char **argv)
rctr = strchr(arg, '(');
if (rctr) {
rctr_end = strchr(rctr, ')');
- if (rctr > rctr_end || *(rctr_end + 1) != 0) {
+ if (!rctr_end || rctr > rctr_end || *(rctr_end + 1) != 0) {
ret = -EINVAL;
pr_info("Invalid reference counter offset.\n");
goto fail_address_parse;
--
2.17.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] tracing: fix potential null pointer dereference on rctr_end
2018-09-27 22:47 [PATCH] tracing: fix potential null pointer dereference on rctr_end Colin King
@ 2019-03-28 0:37 ` Steven Rostedt
0 siblings, 0 replies; 2+ messages in thread
From: Steven Rostedt @ 2019-03-28 0:37 UTC (permalink / raw)
To: Colin King; +Cc: Ingo Molnar, kernel-janitors, linux-kernel
I just found this in the depths of my inbox (which is now managed by a
local Patchwork system, so no more lost patches!)
On Thu, 27 Sep 2018 23:47:00 +0100
Colin King <colin.king@canonical.com> wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> Currently rctr_end may assigned null if strchr() fails leading to
> a null pointer dereference in the following check on *(rctr_end + 1).
> Fix this by also adding a null pointer check before the dereference.
>
> Detected by CoverityScan, CID#1473700 ("Dereference null return value")
>
> Fixes: 1cc33161a83d ("uprobes: Support SDT markers having reference count (semaphore)")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
> kernel/trace/trace_uprobe.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 3a7c73c40007..c5514651e61f 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -477,7 +477,7 @@ static int create_trace_uprobe(int argc, char **argv)
> rctr = strchr(arg, '(');
> if (rctr) {
> rctr_end = strchr(rctr, ')');
> - if (rctr > rctr_end || *(rctr_end + 1) != 0) {
> + if (!rctr_end || rctr > rctr_end || *(rctr_end + 1) != 0) {
I think this is a false positive.
rctr and rctr_end are pointers. Thus, they are compared as unsigned.
To get into this code, rctr must be non NULL (greater than zero)
The first compare of the if conditional is:
rctr > rctr_end
If rctr_end is NULL, then that is guaranteed to be true!
Which means, the rctr_end will not be access, and we exit out safely.
-- Steve
> ret = -EINVAL;
> pr_info("Invalid reference counter offset.\n");
> goto fail_address_parse;
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