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tools: Fix use of fcntl(F_SETFD) during socket activation 

Blindly setting FD_CLOEXEC without a read-modify-write will
inadvertently clear any other intentionally-set bits, such as a
proposed new bit for designating a fd that must behave in 32-bit mode.
However, we cannot use our wrapper qemu_set_cloexec(), because that
wrapper intentionally abort()s on failure, whereas the probe here
intentionally tolerates failure to deal with incorrect socket
activation gracefully.  Instead, fix the code to do the proper
read-modify-write.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200420175309.75894-3-eblake@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Eric Blake 2020-04-20 12:53:08 -05:00
parent 5375af3cd7
commit 474a6e64f2
1 changed files with 3 additions and 1 deletions
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4
util/systemd.c
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@ -23,6 +23,7 @@ unsigned int check_socket_activation(void)
unsigned long nr_fds;
unsigned int i;
int fd;
int f;
int err;
s = getenv("LISTEN_PID");
@ -54,7 +55,8 @@ unsigned int check_socket_activation(void)
/* So the file descriptors don't leak into child processes. */
for (i = 0; i < nr_fds; ++i) {
fd = FIRST_SOCKET_ACTIVATION_FD + i;
if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) {
f = fcntl(fd, F_GETFD);
if (f == -1 || fcntl(fd, F_SETFD, f | FD_CLOEXEC) == -1) {
/* If we cannot set FD_CLOEXEC then it probably means the file
* descriptor is invalid, so socket activation has gone wrong
* and we should exit.