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sd-varlink: fix fd handling in upgrade code path

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This commit fixes an issue with the fd handling in
sd_varlink_call_and_upgrade() when one direction of the output
FDs is unset.

Thanks to Lennart for spotting this and suggesting the fix.
This commit is contained in:
Michael Vogt
2026-04-02 13:20:17 +02:00
committed by Daan De Meyer
parent 73c0a79789
commit f180ff5983
1 changed files with 15 additions and 11 deletions
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src/libsystemd/sd-varlink/sd-varlink.c
+15 -11
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@@ -2452,26 +2452,30 @@ _public_ int sd_varlink_call_and_upgrade(
}
}
/* Handle the case where the caller is not interested in one of the fds. We need
* to consider the case when (input_fd == output_fd) just clear the alias
* rather than closing it, since the other branch may hand it out. */
/* Hand out the fds to the caller. When the caller doesn't want one direction, shut it
* down: but avoid closing the underlying fd if the other direction still needs it
* (i.e. when input_fd == output_fd). */
bool same_fd = v->input_fd == v->output_fd;
if (ret_input_fd)
*ret_input_fd = TAKE_FD(v->input_fd);
else if (!same_fd) {
else {
(void) shutdown(v->input_fd, SHUT_RD);
v->input_fd = safe_close(v->input_fd);
} else
v->input_fd = -EBADF;
if (same_fd && ret_output_fd)
TAKE_FD(v->input_fd); /* don't close yet, output branch needs it */
else
v->input_fd = safe_close(v->input_fd);
}
if (ret_output_fd)
*ret_output_fd = TAKE_FD(v->output_fd);
else if (!same_fd) {
else {
(void) shutdown(v->output_fd, SHUT_WR);
v->output_fd = safe_close(v->output_fd);
} else
v->output_fd = -EBADF;
if (same_fd && ret_input_fd)
TAKE_FD(v->output_fd);
else
v->output_fd = safe_close(v->output_fd);
}
varlink_set_state(v, VARLINK_DISCONNECTED);
assert(v->n_pending == 1);