linux-kernel - [PATCH v2 1/4] kstrtox: always skip the leading "0x" even if no more valid chars

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Date: Tue,  2 Jan 2024 14:42:11 +1030
From: Qu Wenruo <wqu@...e.com>
To: linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org,
	christophe.jaillet@...adoo.fr,
	andriy.shevchenko@...ux.intel.com,
	David.Laight@...LAB.COM,
	ddiss@...e.de
Subject: [PATCH v2 1/4] kstrtox: always skip the leading "0x" even if no more valid chars

Currently the invalid string "0x" (only hex prefix, no valid chars
followed) would make _parse_integer_fixup_radix() to treat it as octal.

This is due to the fact that the function would only auto-detect hex if
and only if there is any valid hex char after "0x".
Or it would only go octal instead.

Thankfully this won't affect our unit test, as "0x" would still be
treated as failure.
Since we treat the result as octal, the result value would be 0, leaving
"x" as the tailing char and still fail kstrtox() functions.

But for the incoming memparse_safe(), the remaining string would still
be consumed by the caller, and we need to properly treat "0x" as an
invalid string.

So this patch would make _parse_integer_fixup_radix() to forcefully go
hex no matter if there is any valid char following.

Signed-off-by: Qu Wenruo <wqu@...e.com>
---
 lib/kstrtox.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/kstrtox.c b/lib/kstrtox.c
index d586e6af5e5a..41c9a499bbf3 100644
--- a/lib/kstrtox.c
+++ b/lib/kstrtox.c
@@ -27,7 +27,7 @@ const char *_parse_integer_fixup_radix(const char *s, unsigned int *base)
 {
 	if (*base == 0) {
 		if (s[0] == '0') {
-			if (_tolower(s[1]) == 'x' && isxdigit(s[2]))
+			if (_tolower(s[1]) == 'x')
 				*base = 16;
 			else
 				*base = 8;
-- 
2.43.0