The existing code attempted to handle numbers by doing a strto[u]l(),
ignoring the field width, and then repeatedly dividing to extract the
field out of the full converted value. If the string contains a run of
valid digits longer than will fit in a long or long long, this would
overflow and no amount of dividing can recover the correct value.
This patch fixes vsscanf() to obey number field widths when parsing
the number.
A new _parse_integer_limit() is added that takes a limit for the number
of characters to parse. The number field conversion in vsscanf is changed
to use this new function.
If a number starts with a radix prefix, the field width must be long
enough for at last one digit after the prefix. If not, it will be handled
like this:
sscanf("0x4", "%1i", ): i=0, scanning continues with the 'x'
sscanf("0x4", "%2i", ): i=0, scanning continues with the '4'
This is consistent with the observed behaviour of userland sscanf.
Note that this patch does NOT fix the problem of a single field value
overflowing the target type. So for example:
sscanf("123456789abcdef", "%x", );
Will not produce the correct result because the value obviously overflows
INT_MAX. But sscanf will report a successful conversion.
Note that where a very large number is used to mean "unlimited", the value
INT_MAX is used for consistency with the behaviour of vsnprintf().
Signed-off-by: Richard Fitzgerald
---
Changed since v5:
- Use INT_MAX to mean "unlimited length".
- Rework simple_strntoull() to avoid the goto
- Rewrite the comment in simple_strntoll()
- In vsscanf() change the calls to simple_strnto[u]ll() so that a field_width
of 0 is not treated as unlimited.
Changed since v3:
- Use INT_MAX to mean "unlimited length".
- Use while-loop instead of for-loop in _parse_integer_limit().
- Keep the existing arguments for _parse_integer() on their original line.
And the corresponding arguments to _parse_integer_limit() formatted/wrapped
the same way as _parse_integer().
- Remove redundant check for (max_chars == 0) in simple_strntoull().
- Fixed "vsscanf" -> "vsscanf()" in commit message.
---
lib/kstrtox.c | 13 ++--
lib/kstrtox.h | 2 ++
lib/vsprintf.c | 88 +-
3 files changed, 63 insertions(+), 40 deletions(-)
diff --git a/lib/kstrtox.c b/lib/kstrtox.c
index a118b0b1e9b2..0b5fe8b41173 100644
--- a/lib/kstrtox.c
+++ b/lib/kstrtox.c
@@ -39,20 +39,22 @@ const char *_parse_integer_fixup_radix(const char *s,
unsigned int *base)
/*
* Convert non-negative integer string representation in explicitly given radix
- * to an integer.
+ * to an integer. A maximum of max_chars characters will be converted.
+ *
* Return number of characters consumed maybe or-ed with overflow bit.
* If overflow occurs, result integer (incorrect) is still returned.
*
* Don't you dare use this function.
*/
-unsigned int _parse_integer(const char *s, unsigned int base, unsigned long
long *p)
+unsigned int _parse_integer_limit(const char *s, unsigned int base, unsigned
long long *p,
+ size_t max_chars)
{
unsigned long long res;
unsigned int rv;
res = 0;
rv = 0;
- while (1) {
+ while (max_chars--) {
unsigned int c = *s;
unsigned int lc = c | 0x20; /* don't tolower() this line */
unsigned int val;
@@ -82,6 +84,11 @@ unsigned int _parse_integer(const char *s, unsigned int
base, unsigned long long
return rv;
}
+unsigned int _parse_integer(const char *s, unsigned int base, unsigned long
long *p)
+{
+ return _parse_integer_limit(s, base, p, INT_MAX);
+}
+
static int _kstrtoull(const char *s, unsigned int base, unsigned long long
*res)
{
unsigned long long _res;
diff --git a/lib/kstrtox.h b/lib/kstrtox.h
index 3b4637bcd254..158c400ca865 100644
--- a/lib/kstrtox.h
+++ b/lib/kstrtox.h
@@ -4,6 +4,8 @@
#define KSTRTOX_OVERFLOW (1U << 31)
const char *_parse_integer_fixup_radix(const char *s, unsigned int *base);
+unsigned int _parse_integer_limit(const char *s, unsigned int base, unsigned
long long *res,
+ size_t max_chars);
unsigned int _parse_integer(const char *s, unsigned int base, unsigned long
long *res);
#endif
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 28bb26cd1f67..794ecc373bf9 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -53,29 +53,43 @@
#include
#include "kstrtox.h"
-/**
- * simple_strtoull - convert a string to an unsigned long long
- * @cp: The start of the string
- * @endp: A pointer to the end of the parsed string will be placed here
- * @base: The number base to use
- *
- * This function has caveats. Please use kstrtoull instead.
- */
-unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int
base)
+static unsigned long long simple_strntoull(const char *startp, size_t
max_chars,
+ char
