Messages in this thread Patch in this message | | | From | Richard Fitzgerald <> | Subject | [PATCH] lib: vsprintf: Avoid 32-bit truncation in vsscanf number parsing | Date | Thu, 12 Nov 2020 11:17:59 +0000 |
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Number conversion in vsscanf converts a whole string of digits and then extracts the field width part from the converted value. The maximum run of digits is limited by overflow. Conversion was using either simple_strto[u]l or simple_strto[u]ll based on the 'L' qualifier. This created a difference in truncation between builds where long is 32-bit and builds where it is 64-bit. This especially affects parsing a run of contiguous digits into separate fields - the maximum length of the run is 16 digits if long is 64-bit but only 8 digits if long is 32-bits. For example a conversion "%6x%6x" would convert both fields correctly if long is 64-bit but not if long is 32-bit.
It is undesirable for vsscanf to parse numbers differently depending on the size of long on the target build.
As simple_strto[u]l just calls simple_strto[u]ll anyway the conversion is always 64-bit, and the result is manipulated as a u64, so this is an avoidable behaviour difference between 32-bit and 64-bit builds. The conversion can call simple_strto[u]ll directly and preserve the full 64-bits that were parsed out of the string.
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com> --- lib/vsprintf.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 14c9a6af1b23..63b6cddfa7f7 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -3444,13 +3444,9 @@ int vsscanf(const char *buf, const char *fmt, va_list args) break; if (is_sign) - val.s = qualifier != 'L' ? - simple_strtol(str, &next, base) : - simple_strtoll(str, &next, base); + val.s = simple_strtoll(str, &next, base); else - val.u = qualifier != 'L' ? - simple_strtoul(str, &next, base) : - simple_strtoull(str, &next, base); + val.u = simple_strtoull(str, &next, base); if (field_width > 0 && next - str > field_width) { if (base == 0) -- 2.20.1
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