Patchwork [MTD-UTILS] Incorrect loop condition

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Submitter Nahor
Date June 4, 2009, 1:18 a.m.
Message ID <h077d2$ra9$1@ger.gmane.org>
Download mbox | patch
Permalink /patch/28083/
State New
Headers show

Comments

Nahor - June 4, 2009, 1:18 a.m.
Hi all,

Here is a small patch to fix an obvious typo.

If the file contains only a few bytes in the last page and the padding 
option is selected, the loop may exit early (readlen < meminfo.oobsize).
Most of the time it will still work though because the code tries to 
read the whole OOB in one chunk.


On a similar issue, shouldn't the loop reading the input file exit with 
error if cnt == 0? The loop should alread exit when all the expected 
data is read. So if cnt == 0, it means that nandwrite didn't get all the 
data it wanted. The code then goes on as if everything was correctly 
read so it will write the data from the previous page. This is a 
security risk (even though the necessary conditions make it nearly 
impossible in practice).


Regards,
    Nahor



                                        break;
Artem Bityutskiy - June 5, 2009, 12:15 p.m.
On Wed, 2009-06-03 at 18:18 -0700, Nahor wrote:
> --- a/nandwrite.c        2009-06-01 18:03:55.000000000 -0700
> +++ b/nandwrite.c 2009-06-03 15:29:24.000000000 -0700
> @@ -531,7 +531,7 @@
>                 if (writeoob) {
>                         int tinycnt = 0;
> 
> -                       while(tinycnt < readlen) {
> +                       while(tinycnt < meminfo.oobsize) {
>                                 cnt = read(ifd, oobreadbuf + tinycnt,
> meminfo.oobsize - tinycnt);
>                                 if (cnt == 0) { // EOF
>                                         break;
> 

This looks valid for me. Would you please, send a patch which I can
apply, which would include your name and Signed-off-by signature?

Patch

--- a/nandwrite.c        2009-06-01 18:03:55.000000000 -0700
+++ b/nandwrite.c 2009-06-03 15:29:24.000000000 -0700
@@ -531,7 +531,7 @@ 
                if (writeoob) {
                        int tinycnt = 0;

-                       while(tinycnt < readlen) {
+                       while(tinycnt < meminfo.oobsize) {
                                cnt = read(ifd, oobreadbuf + tinycnt,
meminfo.oobsize - tinycnt);
                                if (cnt == 0) { // EOF