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fd-util: rework how we determine highest possible fd

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This commit is contained in:
Lennart Poettering 2019-01-17 12:23:21 +01:00
parent 99a2fd3bca
commit 498e265df1
1 changed files with 26 additions and 11 deletions
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37
src/basic/fd-util.c
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@ -189,6 +189,27 @@ _pure_ static bool fd_in_set(int fd, const int fdset[], size_t n_fdset) {
return false;
}
static int get_max_fd(void) {
struct rlimit rl;
rlim_t m;
/* Return the highest possible fd, based RLIMIT_NOFILE, but enforcing FD_SETSIZE-1 as lower boundary
* and INT_MAX as upper boundary. */
if (getrlimit(RLIMIT_NOFILE, &rl) < 0)
return -errno;
m = MAX(rl.rlim_cur, rl.rlim_max);
if (m < FD_SETSIZE) /* Let's always cover at least 1024 fds */
return FD_SETSIZE-1;
if (m == RLIM_INFINITY || m > INT_MAX) /* Saturate on overflow. After all fds are "int", hence can
* never be above INT_MAX */
return INT_MAX;
return (int) (m - 1);
}
int close_all_fds(const int except[], size_t n_except) {
_cleanup_closedir_ DIR *d = NULL;
struct dirent *de;
@ -198,20 +219,14 @@ int close_all_fds(const int except[], size_t n_except) {
d = opendir("/proc/self/fd");
if (!d) {
struct rlimit rl;
int fd, max_fd;
/* When /proc isn't available (for example in chroots) the fallback is brute forcing through the fd
* table */
/* When /proc isn't available (for example in chroots) the fallback is brute forcing through
* the fd table */
assert_se(getrlimit(RLIMIT_NOFILE, &rl) >= 0);
if (rl.rlim_max == 0)
return -EINVAL;
/* Let's take special care if the resource limit is set to unlimited, or actually larger than the range
* of 'int'. Let's avoid implicit overflows. */
max_fd = (rl.rlim_max == RLIM_INFINITY || rl.rlim_max > INT_MAX) ? INT_MAX : (int) (rl.rlim_max - 1);
max_fd = get_max_fd();
if (max_fd < 0)
return max_fd;
for (fd = 3; fd >= 0; fd = fd < max_fd ? fd + 1 : -1) {
int q;