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hex2bin: fix access beyond string end

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commit e4d8a29997 upstream.

If we pass too short string to "hex2bin" (and the string size without
the terminating NUL character is even), "hex2bin" reads one byte after
the terminating NUL character.  This patch fixes it.

Note that hex_to_bin returns -1 on error and hex2bin return -EINVAL on
error - so we can't just return the variable "hi" or "lo" on error.
This inconsistency may be fixed in the next merge window, but for the
purpose of fixing this bug, we just preserve the existing behavior and
return -1 and -EINVAL.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Fixes: b78049831f ("lib: add error checking to hex2bin")
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mikulas Patocka 2022-04-27 11:26:40 -04:00 • committed by Justin Hammond
parent 8a896162f6
commit 0cd480bcc7
1 changed files with 6 additions and 3 deletions
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9
lib/hexdump.c
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@ -63,10 +63,13 @@ EXPORT_SYMBOL(hex_to_bin);
int hex2bin(u8 *dst, const char *src, size_t count)
{
while (count--) {
int hi = hex_to_bin(*src++);
int lo = hex_to_bin(*src++);
int hi, lo;
if ((hi < 0) || (lo < 0))
hi = hex_to_bin(*src++);
if (unlikely(hi < 0))
return -EINVAL;
lo = hex_to_bin(*src++);
if (unlikely(lo < 0))
return -EINVAL;
*dst++ = (hi << 4) | lo;