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libc/minimal: snprintf(): KILL negative len parameter

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snprintf() implements the ability to foce a negative value through the
(unsigned) size_t len parameter to allow the formatter to use a
maximum size string.

This is point less, we don't have as much memory and this is a recipe
for all kinds of vulnerabilities.

Kill the whole thing, the testcase it represents and thank Coverity
for finding this thing. Whatever use it had before, it has no more.

Change-Id: If422246548664699d8aa328a1b9304ef13cab7ea
Coverity-ID: 131625
Coverity-ID: 131626
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
This commit is contained in:
Inaky Perez-Gonzalez 2016-11-22 11:20:55 -08:00 • committed by Anas Nashif
commit b53e6d7774
2 changed files with 4 additions and 53 deletions
Download patch file Download diff file Expand all files Collapse all files

16
lib/libc/minimal/source/stdout/sprintf.c
View file

@ -45,12 +45,8 @@ int snprintf(char *_Restrict s, size_t len, const char *_Restrict format, ...)
int r;
char dummy;
if ((int) len <= 0) {
if (len == 0) {
s = &dummy; /* write final NUL to dummy, since can't change *s */
} else {
len = 0x7fffffff; /* allow up to "maxint" characters */
}
if (len == 0) {
s = &dummy; /* write final NUL to dummy, can't change *s */
}
p.ptr = s;
@ -88,12 +84,8 @@ int vsnprintf(char *_Restrict s, size_t len, const char *_Restrict format, va_li
int r;
char dummy;
if ((int) len <= 0) {
if (len == 0) {
s = &dummy; /* write final NUL to dummy, since can't change *s */
} else {
len = 0x7fffffff; /* allow up to "maxint" characters */
}
if (len == 0) {
s = &dummy; /* write final NUL to dummy, can't change * *s */
}
p.ptr = s;

41
tests/kernel/test_sprintf/src/test_sprintf.c
View file

@ -235,27 +235,6 @@ int vsnprintfTest(void)
int status = TC_PASS;
char buffer[100];
/*
* The string size may be handled in a non-standard manner.
* If a negative value is supplied for the string size, it is converted
* to 0x7fffffff--maximum integer size. Since there is insufficient
* memory to test a string of that length, we just check that the string
* was fully written so that we can exercise the code path.
*/
buffer[0] = '\0';
len = tvsnprintf(buffer, (size_t)(-4), "%x", DEADBEEF);
if (len != strlen(DEADBEEF_LHEX_STR)) {
TC_ERROR("vsnprintf(%%x). Expected return value %d, not %d\n",
strlen(DEADBEEF_LHEX_STR), len);
status = TC_FAIL;
}
if (strcmp(buffer, DEADBEEF_LHEX_STR) != 0) {
TC_ERROR("vsnprintf(%%x). Expected '%s', got '%s'\n",
DEADBEEF_LHEX_STR, buffer);
status = TC_FAIL;
}
/*******************/
buffer[0] = '\0';
len = tvsnprintf(buffer, 0, "%x", DEADBEEF);
@ -356,26 +335,6 @@ int snprintfTest(void)
int status = TC_PASS;
char buffer[100];
/*
* The string size may be handled in a non-standard manner.
* If a negative value is supplied for the string size, it is converted
* to 0x7fffffff--maximum integer size. Since there is insufficient
* memory to test a string of that length, we just check that the string
* was fully written so that we can exercise the code path.
*/
buffer[0] = '\0';
len = snprintf(buffer, (size_t)(-4), "%x", DEADBEEF);
if (len != strlen(DEADBEEF_LHEX_STR)) {
TC_ERROR("snprintf(%%x). Expected return value %d, not %d\n",
strlen(DEADBEEF_LHEX_STR), len);
status = TC_FAIL;
}
if (strcmp(buffer, DEADBEEF_LHEX_STR) != 0) {
TC_ERROR("snprintf(%%x). Expected '%s', got '%s'\n",
DEADBEEF_LHEX_STR, buffer);
status = TC_FAIL;
}
/*******************/
buffer[0] = '\0';