Commit 2a2806bb authored Dec 28, 2024 by Chris Friedt Committed by Henrik Brix Andersen Jan 05, 2025

os: fdtable: restore errno if optional locking ioctl fails

The `zvfs_finalize_typed_fd()` function notifies some backends
via `ioctl()` with `ZFD_IOCTL_SET_LOCK`. However, support for
this method and functionality is optional.

In backends that do not support locking, this benign failure can
set `errno` to 95 (`EOPNOTSUPP`) in many circumstances where a
change in `errno` (indicating some kind of failure) is not
appropriate.

Prevent errno poisoning by backing-up and restoring `errno`.

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>

parent ba8025fc

lib/os/fdtable.c

+6 −0

Changes for lib/os/fdtable.c: 6 added lines, 0 removed lines.
Original line number	Diff line number	Diff line
		@@ -280,8 +280,14 @@ void zvfs_finalize_typed_fd(int fd, void obj, const struct fd_op_vtable vtable
		* variables to avoid keeping the lock for a long period of time.
		*/
		if (vtable && vtable->ioctl) {
		int prev_errno = errno;

		(void)zvfs_fdtable_call_ioctl(vtable, obj, ZFD_IOCTL_SET_LOCK,
		&fdtable[fd].lock);
		if ((prev_errno != EOPNOTSUPP) && (errno == EOPNOTSUPP)) {
		/* restore backed-up errno value if the backend does not support locking */
		errno = prev_errno;
		}
		}
		}

Admin message