selftests: Fix errno checking in syscall_user_dispatch test

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[ Upstream commit b89732c8c8 ]

Successful syscalls don't change errno, so checking errno is wrong
to ensure that a syscall has failed. For example for the following
sequence:

	prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0xff, 0);
	EXPECT_EQ(EINVAL, errno);
	prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0x0, &sel);
	EXPECT_EQ(EINVAL, errno);

only the first syscall may fail and set errno, but the second may succeed
and keep errno intact, and the check will falsely pass.
Or if errno happened to be EINVAL before, even the first check may falsely
pass.

Also use EXPECT/ASSERT consistently. Currently there is an inconsistent mix
without obvious reasons for usage of one or another.

Fixes: 179ef03599 ("selftests: Add kselftest for syscall user dispatch")
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/af6a04dbfef9af8570f5bab43e3ef1416b62699a.1747839857.git.dvyukov@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

...

This commit is contained in:

Dmitry Vyukov 2025-05-21 17:04:28 +02:00 • committed by Greg Kroah-Hartman

parent c814023c82

commit 90040a4803

1 changed files with 25 additions and 25 deletions

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tools/testing/selftests/syscall_user_dispatch/sud_test.c

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