2018-05-17 12:24:52

by Dan Carpenter

Subject: [PATCH] misc: kgdbts: silence array underflow warning

Smatch distrusts simple_strtol(). I don't know the code well enough
to say if the distrust is justified here, but it seems harmless to
silence the warning.

Signed-off-by: Dan Carpenter <[email protected]>

diff --git a/drivers/misc/kgdbts.c b/drivers/misc/kgdbts.c
index 6193270e7b3d..e0508acaedaa 100644
--- a/drivers/misc/kgdbts.c
+++ b/drivers/misc/kgdbts.c
@@ -400,13 +400,15 @@ static void skip_back_repeat_test(char *arg)
int go_back = simple_strtol(arg, NULL, 10);

repeat_test--;
- if (repeat_test <= 0) {
+ if (repeat_test <= 0 || go_back < 0) {
ts.idx++;
} else {
if (repeat_test % 100 == 0)
v1printk("kgdbts:RUN ... %d remaining\n", repeat_test);

ts.idx -= go_back;
+ if (ts.idx < 0)
+ ts.idx = 0;
}
fill_get_buf(ts.tst[ts.idx].get);
}

2018-05-17 13:33:01

by Daniel Thompson

Subject: Re: [PATCH] misc: kgdbts: silence array underflow warning

On Thu, May 17, 2018 at 03:22:29PM +0300, Dan Carpenter wrote:
> Smatch distrusts simple_strtol(). I don't know the code well enough
> to say if the distrust is justified here, but it seems harmless to
> silence the warning.

What warning does this fix? I'd prefer to have it in the description.


> Signed-off-by: Dan Carpenter <[email protected]>
>
> diff --git a/drivers/misc/kgdbts.c b/drivers/misc/kgdbts.c
> index 6193270e7b3d..e0508acaedaa 100644
> --- a/drivers/misc/kgdbts.c
> +++ b/drivers/misc/kgdbts.c
> @@ -400,13 +400,15 @@ static void skip_back_repeat_test(char *arg)
> int go_back = simple_strtol(arg, NULL, 10);

If go_back is out of range then this is a serious error in the test
plans found in the module. Something simple and clear such as
BUG_ON(go_back <= 0 || go_back > ts.idx) is probably sufficient.


> repeat_test--;
> - if (repeat_test <= 0) {
> + if (repeat_test <= 0 || go_back < 0) {

The BUG_ON() will mess things up because whatever breakpoints
the test is using are still enabled.

If you really want to recover cleanly then perhaps:

+ if (repeat_test <= 0 || WARN_ON(go_back < 0 || go_back > ts.idx)) {


> ts.idx++;
> } else {
> if (repeat_test % 100 == 0)
> v1printk("kgdbts:RUN ... %d remaining\n", repeat_test);
>
> ts.idx -= go_back;
> + if (ts.idx < 0)
> + ts.idx = 0;

Not sure about this. If we know the opcodes are bad then re-executing
them doesn't seem like a good idea (hence covering it in the WARN_ON
branch above).


Daniel.