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author | Richard Fitzgerald <rf@opensource.cirrus.com> | 2021-05-14 19:12:04 +0300 |
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committer | Petr Mladek <pmladek@suse.com> | 2021-05-19 16:05:11 +0300 |
commit | 900fdc4573766dd43b847b4f54bd4a1ee2bc7360 (patch) | |
tree | e016b94ba7ea217afa3f9894cbf95fa2bf86bc4b /lib/kstrtox.c | |
parent | 11b3dda5e8b6cde957a6410233f30d6c48582998 (diff) | |
download | linux-900fdc4573766dd43b847b4f54bd4a1ee2bc7360.tar.xz |
lib: vsprintf: Fix handling of number field widths in vsscanf
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): i=0, scanning continues with the 'x'
sscanf("0x4", "%2i", &i): 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", &i);
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 <rf@opensource.cirrus.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210514161206.30821-2-rf@opensource.cirrus.com
Diffstat (limited to 'lib/kstrtox.c')
-rw-r--r-- | lib/kstrtox.c | 13 |
1 files changed, 10 insertions, 3 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; |