> -----Original Message-----
> From: Gaëtan Rivet [mailto:gaetan.ri...@6wind.com]
> Sent: Thursday, August 17, 2017 6:26 PM
> To: Matan Azrad <ma...@mellanox.com>
> Cc: dev@dpdk.org; Ori Kam <or...@mellanox.com>; sta...@dpdk.org
> Subject: Re: [PATCH] net/failsafe: fix parameters parsing
>
> Hi Matan,
>
> Thanks for spotting the bug.
>
> On Thu, Aug 17, 2017 at 05:19:41PM +0300, Matan Azrad wrote:
> > The corrupted code used wrongly snprintf return value as the number of
> > characters actually copied, in spite of the meanning is the number of
> > characters which would be generated for the given input.
> >
> > It caused to remain zerod bytes between the failsafe command line non
> > sub device parameters indicates end of string.
> >
> > Hence, when rte_kvargs_parse tried to parse all parameters, it got end
> > of string after the first one and the others weren't parsed.
> >
> > So, if the mac parameters was the first in command line it was taken
> > while hotplug_poll was left default, and vice versa.
> >
> > The fix updates the buffer index by dedicated variable contains the
> > copy size, by the way uses memcpy instead of snprintf which is good
> > enouth for this copy scenario.
>
> Actually snprintf should still be used.
>
Why?
We just want to copy from buffer to buffer, no needs snprintf overheads
If actually we are not using complicated format.
> >
> > Fixes: a46f8d584eb8 ("net/failsafe: add fail-safe PMD")
> > Cc: sta...@dpdk.org
> >
> > Signed-off-by: Matan Azrad <ma...@mellanox.com>
> > ---
> > drivers/net/failsafe/failsafe_args.c | 14 ++++++++------
> > 1 file changed, 8 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/net/failsafe/failsafe_args.c
> > b/drivers/net/failsafe/failsafe_args.c
> > index 1f22416..0a98b04 100644
> > --- a/drivers/net/failsafe/failsafe_args.c
> > +++ b/drivers/net/failsafe/failsafe_args.c
> > @@ -271,7 +271,7 @@ static int
> > fs_remove_sub_devices_definition(char params[DEVARGS_MAXLEN]) {
> > char buffer[DEVARGS_MAXLEN] = {0};
> > - size_t a, b;
> > + size_t a, b, temp;
>
> temp is not descriptive enough.
What are about a, b, i ?
> You are declaring this variable here because you want to re-use it instead of
> `start`. This is an overreach however, this fix must be restricted to the
> actual
> bug.
temp is helping to address the original bug, don't we want to reuse variable
Instead of 2 if statement variables, maybe other name for all?
Something like:
a=> start
b=> end
i => next
temp=> saved_val
>
> > int i;
> >
> > a = 0;
> > @@ -286,12 +286,14 @@ fs_remove_sub_devices_definition(char
> params[DEVARGS_MAXLEN])
> > ERROR("Invalid parameter");
> > return -EINVAL;
> > }
> > - if (params[b] == ',' || params[b] == '\0')
>
> Declare the temporary variable in this scope, with a descriptive name such as
> "len", "length", "param_len" or something close.
>
> > - i += snprintf(&buffer[i], b - a + 1, "%s", ¶ms[a]);
> > - if (params[b] == '(') {
> > - size_t start = b;
> > + if (params[b] == ',' || params[b] == '\0') {
> > + temp = b - a + 1;
>
> The value here should be "b - a".
> If a != 0 however, then we are parsing a new parameter and buffer already
> contains at least one. A comma should be added to separate the two.
>
> An example might clarify what I mean:
>
> if (params[b] == ',' || params[b] == '\0') {
> size_t param_len = b - a;
>
> if (a)
> param_len += 1;
> snprintf(&buffer[i], param_len + 1, "%s%s",
> a ? "," : "", ¶ms[a]);
> i += param_len;
> }
>
> The conditionals about `a` are ugly however, if you find a better way to write
> those you are most welcome :).
>
> > + memcpy(&buffer[i], ¶ms[a], temp);
> > + i += temp;
> > + } else if (params[b] == '(') {
> > + temp = b;
> > b += closing_paren(¶ms[b]);
> > - if (b == start)
>
I think the last comma is harmless for next parse
But I can just change the last coma to '\0' in the end of function(if exists).
But, This solves another issue, don't it? Maybe in different patch?
> The changes should be limited to the actual bug. No need to change this.
>
> > + if (b == temp)
> > return -EINVAL;
> > b += 1;
> > if (params[b] == '\0')
> > --
> > 2.7.4
> >
>
> Thanks again for the debug and sorry for being nitpicky.
>
> --
> Gaëtan Rivet
> 6WIND
Regards,
Matan Azrad.
