uevent: make it survive ENOBUFS
function old new delta
uevent_main 285 337 +52
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/util-linux/uevent.c b/util-linux/uevent.c
index 2f1135f..045b354 100644
--- a/util-linux/uevent.c
+++ b/util-linux/uevent.c
@@ -30,19 +30,19 @@
#define INIT_G() do { setup_common_bufsiz(); } while (0)
enum {
MAX_ENV = COMMON_BUFSIZE / sizeof(char*) - 1,
- /* sizeof(env[0]) instead of sizeof(char*)
- * makes gcc-6.3.0 emit "strict-aliasing" warning.
- */
-};
+ // ^^^sizeof(env[0]) instead of sizeof(char*)
+ // makes gcc-6.3.0 emit "strict-aliasing" warning.
-enum {
- /* socket receive buffer of 2MiB proved to be too small:
- * http://lists.busybox.net/pipermail/busybox/2019-December/087665.html
- * Udevd seems to use a whooping 128MiB.
- * The socket receive buffer size is just a resource limit.
- * The buffers are allocated lazily so the memory is not wasted.
- */
+ // socket receive buffer of 2MiB proved to be too small:
+ // http://lists.busybox.net/pipermail/busybox/2019-December/087665.html
+ // udevd seems to use a whooping 128MiB.
+ // The socket receive buffer size is just a resource limit.
+ // The buffers are allocated lazily so the memory is not wasted.
KERN_RCVBUF = 128 * 1024 * 1024,
+
+ // Might be made smaller: the kernel v5.4 passes up to 32 environment
+ // variables with a total of 2kb on each event.
+ // On top of that the action string and device path are added.
USER_RCVBUF = 16 * 1024,
};
@@ -61,6 +61,7 @@
// Reproducer:
// uevent mdev &
// find /sys -name uevent -exec sh -c 'echo add >"{}"' ';'
+ reopen:
fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, /*groups:*/ 1 << 0, KERN_RCVBUF);
for (;;) {
@@ -82,8 +83,16 @@
// Here we block, possibly for a very long time
len = safe_read(fd, netbuf, USER_RCVBUF - 1);
- if (len < 0)
+ if (len < 0) {
+ if (errno == ENOBUFS) {
+ // Ran out of socket receive buffer
+ bb_simple_error_msg("uevent overrun");
+ close(fd);
+ munmap(netbuf, USER_RCVBUF);
+ goto reopen;
+ }
bb_simple_perror_msg_and_die("read");
+ }
end = netbuf + len;
*end = '\0';