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xz: Avoid arithmetic on a null pointer 

It's undefined behavior. The result wasn't ever used as it occurred
in the last iteration of a loop.

Clang 17 with -fsanitize=address,undefined:

    $ src/xz/xz --block-list=123
    src/xz/args.c:164:12: runtime error: applying non-zero offset 1
        to null pointer

Fixes: 88ccf47205
Co-authored-by: Sam James <sam@gentoo.org>
(cherry picked from commit 77c8f60547)
(cherry picked from commit 203d482599)
This commit is contained in:
Lasse Collin 2024-04-30 21:41:11 +03:00
parent ecbc34d90b
commit b933ef49a5
1 changed files with 7 additions and 1 deletions
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8
src/xz/args.c
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@ -120,7 +120,13 @@ parse_block_list(const char *str_const)
}
}
str = p + 1;
// Be standards compliant: p + 1 is undefined behavior
// if p == NULL. That occurs on the last iteration of
// the loop when we won't care about the value of str
// anymore anyway. That is, this is done conditionally
// solely for standard conformance reasons.
if (p != NULL)
str = p + 1;
}
// Terminate the array.