On 08/25/2010 06:47 AM, Andrew Morton wrote:
On Tue, 24 Aug 2010 17:42:46 +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 v3:
make handling of single char also uses cn_printf, suggested by Andrew Morton.
Changes since v2:
Introduced generic function cn_printf and make format_corename remember the time
has been expanded, suggested by Olg Nesterov and Neil Horman.
Changes since v1:
This patch allocates corename at runtime, if the replace doesn't have enough
memory, expand the corename dynamically, suggested by Neil Horman.
I've tested with some core_pattern strings, it works fine now.
cool, thanks.
...
-static int format_corename(char *corename, long signr)
+static int format_corename(struct core_name *cn, long signr)
{
const struct cred *cred = current_cred();
const char *pat_ptr = core_pattern;
int ispipe = (*pat_ptr == '|');
- char *out_ptr = corename;
- char *const out_end = corename + CORENAME_MAX_SIZE;
- int rc;
int pid_in_pattern = 0;
+ int err = 0;
+
+ cn->size = CORENAME_MAX_SIZE * atomic_read(&call_count);
+ cn->corename = kmalloc(cn->size, GFP_KERNEL);
+ cn->used = 0;
+
+ if (!cn->corename)
+ return -ENOMEM;
/* Repeat as long as we have more pattern to process and more output
space */
while (*pat_ptr) {
if (*pat_ptr != '%') {
- if (out_ptr == out_end)
- goto out;
- *out_ptr++ = *pat_ptr++;
+ err = cn_printf(cn, "%c", *pat_ptr++);
} else {
switch (*++pat_ptr) {
+ /* single % at the end, drop that */
case 0:
+ err = cn_printf(cn, "%c", '\0');
Confused. Doesn't this bit just add another \0 to the end of an
already-null-terminated string? And then make cn->used get out of sync
with strlen(cn->corename)?
Good catch, I just realized the return value of vsnprintf is not
including the trailing '\0', will follow an updated v5 patch. Thanks Andrew.
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