cb143b979
Denys Vlasenko
2020-11-22
Subject
uevent: make it survive ENOBUFS
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Commit Diff GitHub →
util-linux/uevent.c+22 -13
| @@ -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'; | |