On 08/24/2010 05:18 AM, Andrew Morton wrote:
On Fri, 20 Aug 2010 17:35:58 +0800
Xiaotian Feng<dfeng@xxxxxxxxxx> wrote:
We met a parameter truncated issue, consider following:
echo "|/root/core_pattern_pipe_test %p /usr/libexec/blah-blah-blah \
%s %c %p %u %g 11 12345678901234567890123456789012345678 %t"> \
/proc/sys/kernel/core_pattern
This is okay because the strings is less than CORENAME_MAX_SIZE.
"cat /proc/sys/kernel/core_pattern" shows the whole string. but
after we run core_pattern_pipe_test in man page, we found last
parameter was truncated like below:
argc[10]=<12807486>
The root cause is core_pattern allows % specifiers, which need to be
replaced during parse time, but the replace may expand the strings
to larger than CORENAME_MAX_SIZE. So if the last parameter is %
specifiers, the replace code is using snprintf(out_ptr, out_end - out_ptr, ...),
this will write out of corename array.
Changes since v2:
Introduced generic function cn_printf and make format_corename remember the time
has been expanded.
Changes since v1:
This patch allocates corename at runtime, if the replace doesn't have enough
memory, expand the corename dynamically.
+ if (cn->used == cn->size)
+ if (expand_corename(cn))
+ goto out_fail;
+
+ out_ptr = cn->corename + cn->used;
+ *out_ptr = *pat_ptr++;
+ cn->used++;
- if (out_ptr == out_end)
- goto out;
- *out_ptr++ = '%';
+ if (cn->used == cn->size)
+ if (expand_corename(cn))
+ goto out_fail;
+
+ out_ptr = cn->corename + cn->used;
+ *out_ptr = '%';
+ cn->used++;
+ out_ptr = cn->corename + cn->used;
+ if (cn->used == cn->size)
+ if (expand_corename(cn))
+ goto out_fail;
+
+ out_ptr = cn->corename + cn->used;
*out_ptr = 0;
Quite a bit of code duplication there. A little helper function which
adds a single char to the output would tidy that up.
Yep, this would be much more cleaner ;-)
However I think that if the % and %% handers are converted to call
cn_printf() then the output is always null-terninated and the third
hunk of code above simply becomes unneeded?
You are absolutely right ;-)
Something like this, although I didn't try very hard. Just a
suggestion to work with ;)
Yep, we just need change a little on your patch
- err = cn_printf(cn, "%%");
+ err = cn_printf(cn, "%");
Do you need me to resend a v4 patch?
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
