[LTP] futex_wait06: Add EFAULT error coverage test

[linuxtestproject.agent@gmail.com]

Hi Michael,

On Wed, 27 May 2026 00:49:24 +0300, Michael Menasherov wrote:
> futex_wait06: Add EFAULT error coverage test

[...]

Patches 1-3 look good to me. One comment issue in patch 4 below.

--- [PATCH 4/4] ---

On Wed, 27 May 2026 00:49:27 +0300, Michael Menasherov wrote:
> futex_cmp_requeue03: Add EFAULT error coverage test

> +/*\
> + * Check that futex(FUTEX_CMP_REQUEUE) returns EFAULT when uaddr or
> + * uaddr2 points to unmapped memory, or when uaddr points to memory
> + * without read permission (PROT_NONE).
> + *
> + * get_futex_key() is called for both uaddr and uaddr2 before the
> + * *uaddr == val check; futex_var and val are both FUTEX_INITIALIZER.
> + */

The comment explains the key-ordering for the uaddr2 case but omits why
opflags=0 (no FUTEX_PRIVATE_FLAG) is required. With FUTEX_PRIVATE_FLAG,
get_futex_key(uaddr2) succeeds using a virtual-address key with no
physical page resolution, so the call returns 0 (no waiters) rather than
EFAULT for the "uaddr2 unmapped" and "uaddr PROT_NONE" cases. Please
add a note similar to the one in futex_wake05, e.g.:

  The test uses opflags=0 (no FUTEX_PRIVATE_FLAG) so get_futex_key()
  takes the shared-futex path and resolves the physical page; this
  lookup fails with EFAULT for unmapped and PROT_NONE addresses.

The code itself (opflags=0 in the call) is correct; the comment just
needs to explain why.

---
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