111 lines
4.2 KiB
Diff
111 lines
4.2 KiB
Diff
From c2665abd4cae74f262d9a522b94528841ad141d2 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Tue, 12 Oct 2021 15:53:27 +0200
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Subject: [PATCH] fd-util: split out inner fallback loop of close_all_fds() as
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close_all_fds_without_malloc()
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(cherry picked from commit 11966552a88039869972ca4b450f622664bd1c5e)
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Related: RHEL-18302
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---
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src/basic/fd-util.c | 63 +++++++++++++++++++++++++--------------------
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src/basic/fd-util.h | 1 +
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2 files changed, 36 insertions(+), 28 deletions(-)
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diff --git a/src/basic/fd-util.c b/src/basic/fd-util.c
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index 5d0df11d7e..7e4611dfda 100644
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--- a/src/basic/fd-util.c
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+++ b/src/basic/fd-util.c
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@@ -213,44 +213,51 @@ static int get_max_fd(void) {
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return (int) (m - 1);
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}
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-int close_all_fds(const int except[], size_t n_except) {
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- _cleanup_closedir_ DIR *d = NULL;
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- struct dirent *de;
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- int r = 0;
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+int close_all_fds_without_malloc(const int except[], size_t n_except) {
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+ int max_fd, r = 0;
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assert(n_except == 0 || except);
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- d = opendir("/proc/self/fd");
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- if (!d) {
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- int fd, max_fd;
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+ /* This is the inner fallback core of close_all_fds(). This never calls malloc() or opendir() or so
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+ * and hence is safe to be called in signal handler context. Most users should call close_all_fds(),
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+ * but when we assume we are called from signal handler context, then use this simpler call
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+ * instead. */
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- /* When /proc isn't available (for example in chroots) the fallback is brute forcing through
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- * the fd table */
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+ max_fd = get_max_fd();
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+ if (max_fd < 0)
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+ return max_fd;
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- max_fd = get_max_fd();
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- if (max_fd < 0)
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- return max_fd;
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+ /* Refuse to do the loop over more too many elements. It's better to fail immediately than to
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+ * spin the CPU for a long time. */
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+ if (max_fd > MAX_FD_LOOP_LIMIT)
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+ return log_debug_errno(EPERM,
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+ "Refusing to loop over %d potential fds.",
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+ max_fd);
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- /* Refuse to do the loop over more too many elements. It's better to fail immediately than to
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- * spin the CPU for a long time. */
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- if (max_fd > MAX_FD_LOOP_LIMIT)
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- return log_debug_errno(EPERM,
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- "/proc/self/fd is inaccessible. Refusing to loop over %d potential fds.",
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- max_fd);
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+ for (int fd = 3; fd >= 0; fd = fd < max_fd ? fd + 1 : -1) {
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+ int q;
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- for (fd = 3; fd >= 0; fd = fd < max_fd ? fd + 1 : -1) {
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- int q;
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+ if (fd_in_set(fd, except, n_except))
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+ continue;
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- if (fd_in_set(fd, except, n_except))
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- continue;
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+ q = close_nointr(fd);
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+ if (q < 0 && q != -EBADF && r >= 0)
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+ r = q;
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+ }
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- q = close_nointr(fd);
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- if (q < 0 && q != -EBADF && r >= 0)
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- r = q;
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- }
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+ return r;
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+}
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- return r;
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- }
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+int close_all_fds(const int except[], size_t n_except) {
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+ _cleanup_closedir_ DIR *d = NULL;
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+ struct dirent *de;
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+ int r = 0;
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+
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+ assert(n_except == 0 || except);
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+
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+ d = opendir("/proc/self/fd");
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+ if (!d)
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+ return close_all_fds_without_malloc(except, n_except); /* ultimate fallback if /proc/ is not available */
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FOREACH_DIRENT(de, d, return -errno) {
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int fd = -1, q;
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diff --git a/src/basic/fd-util.h b/src/basic/fd-util.h
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index 8adc959da8..b2837d3588 100644
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--- a/src/basic/fd-util.h
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+++ b/src/basic/fd-util.h
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@@ -54,6 +54,7 @@ int fd_nonblock(int fd, bool nonblock);
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int fd_cloexec(int fd, bool cloexec);
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int close_all_fds(const int except[], size_t n_except);
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+int close_all_fds_without_malloc(const int except[], size_t n_except);
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int same_fd(int a, int b);
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