Re: [PATCH] lib/bitmap.c: return -EINVAL for grouping errors in __bitmap_parselist

[Pan Xinhui]

hi, Yury
        thanks for your nice reply.

On 2015年06月29日 21:39, Yury Norov wrote:

Sometimes the input from user may cause an unexpected result.

Could you please provide specific example?

I wrote some scripts to do some tests about irqs.
echo "1-3," > /proc/irq/<xxx>/smp_affinity_list
this command ends with ',' by mistake.
actually __bitmap_parselist() will report "0-3" for the final result which is 
wrong.

just like __bitmap_parse, we return -EINVAL if there is no avaiable digit in 
each
parsing procedures.

Signed-off-by: Pan Xinhui <xinhuix....@intel.com>

Hello, Pan.

(Adding Alexey Klimov, Rasmus Villemoes)

---
   lib/bitmap.c | 7 +++++--
   1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 64c0926..995fca2 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -504,7 +504,7 @@ static int __bitmap_parselist(const char *buf, unsigned int 
buflen,
           int nmaskbits)
   {
       unsigned a, b;
-    int c, old_c, totaldigits;
+    int c, old_c, totaldigits, ndigits;
       const char __user __force *ubuf = (const char __user __force *)buf;
       int exp_digit, in_range;

@@ -514,6 +514,7 @@ static int __bitmap_parselist(const char *buf, unsigned int 
buflen,
           exp_digit = 1;
           in_range = 0;
           a = b = 0;
+        ndigits = 0;

           /* Get the next cpu# or a range of cpu#'s */
           while (buflen) {
@@ -555,8 +556,10 @@ static int __bitmap_parselist(const char *buf, unsigned 
int buflen,
               if (!in_range)
                   a = b;
               exp_digit = 0;
-            totaldigits++;
+            ndigits++; totaldigits++;

I'm not happy with joining two statements to a single line.
Maybe sometimes it's OK for loop iterators like

     while (a[i][j]) {
         i++; j++;
     }

But here it looks nasty. Anyway, it's minor.

thanks for pointing out my mistake about the code style :)

           }
+        if (ndigits == 0)
+            return -EINVAL;

You can avoid in-loop incrementation of ndigits if you'll
save current totaldigits to ndigits before loop, and check
ndigits against totaldigits after the loop:

     ndigits = totaldigits;
     while (...) {
          ...
         totaldigits++;
     }

     if (ndigits == totaldigits)
         return -EINVAL;

Maybe it's a good point to rework initial __bitmap_parse() similar way...

your advice is a good idea, thanks.
I am also thinking if we can rewrite them into one function for common codes.

thanks for your reply again :)

thanks
xinhui

           if (!(a <= b))
               return -EINVAL;
           if (b >= nmaskbits)
--
1.9.1

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