1 files changed, 22 insertions, 13 deletions

diff --git a/util-linux/uevent.c b/util-linux/uevent.c
index 2f1135f0c..045b35432 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.
-         */
-};
-
-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.
-         */
+        // ^^^sizeof(env[0]) instead of sizeof(char*)
+        // makes gcc-6.3.0 emit "strict-aliasing" warning.
+
+        // 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 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
         // 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 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
 
                 // 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';