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tools/nolibc: avoid error in dup2() if old fd equals new fd

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dup2() allows both 'old' and 'new' to have the same value, which dup3()
does not. If libc dup2() is implemented through the dup3() system call,
then it would incorrectly fail in this case.

Avoid the error by handling old == new explicitly.

Fixes: 30ca20517a ("tools headers: Move the nolibc header from rcutorture to tools/include/nolibc/")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250820-nolibc-dup2-einval-v2-1-807185a45c56@linutronix.de
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
This commit is contained in:
Thomas Weißschuh 2025-08-20 10:29:27 +02:00 committed by Thomas Weißschuh
parent 850047b197
commit d1ff0e2d13
1 changed files with 13 additions and 0 deletions
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13
tools/include/nolibc/sys.h
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@ -238,6 +238,19 @@ static __attribute__((unused))
int sys_dup2(int old, int new)
{
#if defined(__NR_dup3)
int ret, nr_fcntl;
#ifdef __NR_fcntl64
nr_fcntl = __NR_fcntl64;
#else
nr_fcntl = __NR_fcntl;
#endif
if (old == new) {
ret = my_syscall2(nr_fcntl, old, F_GETFD);
return ret < 0 ? ret : old;
}
return my_syscall3(__NR_dup3, old, new, 0);
#elif defined(__NR_dup2)
return my_syscall2(__NR_dup2, old, new);