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-rw-r--r--util-linux/uevent.c50
1 files changed, 29 insertions, 21 deletions
diff --git a/util-linux/uevent.c b/util-linux/uevent.c
index 57d9328ef..db11746d0 100644
--- a/util-linux/uevent.c
+++ b/util-linux/uevent.c
@@ -15,7 +15,7 @@
15//kbuild:lib-$(CONFIG_UEVENT) += uevent.o 15//kbuild:lib-$(CONFIG_UEVENT) += uevent.o
16 16
17//usage:#define uevent_trivial_usage 17//usage:#define uevent_trivial_usage
18//usage: "[PROG [ARGS]]" 18//usage: "[PROG ARGS]"
19//usage:#define uevent_full_usage "\n\n" 19//usage:#define uevent_full_usage "\n\n"
20//usage: "uevent runs PROG for every netlink notification." 20//usage: "uevent runs PROG for every netlink notification."
21//usage: "\n""PROG's environment contains data passed from the kernel." 21//usage: "\n""PROG's environment contains data passed from the kernel."
@@ -26,22 +26,26 @@
26#include "common_bufsiz.h" 26#include "common_bufsiz.h"
27#include <linux/netlink.h> 27#include <linux/netlink.h>
28 28
29#define BUFFER_SIZE 16*1024
30
31#define env ((char **)bb_common_bufsiz1) 29#define env ((char **)bb_common_bufsiz1)
32#define INIT_G() do { setup_common_bufsiz(); } while (0) 30#define INIT_G() do { setup_common_bufsiz(); } while (0)
33enum { 31enum {
34 MAX_ENV = COMMON_BUFSIZE / sizeof(char*) - 1, 32 MAX_ENV = COMMON_BUFSIZE / sizeof(char*) - 1,
35 /* sizeof(env[0]) instead of sizeof(char*) 33 // ^^^sizeof(env[0]) instead of sizeof(char*)
36 * makes gcc-6.3.0 emit "strict-aliasing" warning. 34 // makes gcc-6.3.0 emit "strict-aliasing" warning.
37 */ 35
36 // socket receive buffer of 2MiB proved to be too small:
37 // http://lists.busybox.net/pipermail/busybox/2019-December/087665.html
38 // udevd seems to use a whooping 128MiB.
39 // The socket receive buffer size is just a resource limit.
40 // The buffers are allocated lazily so the memory is not wasted.
41 KERN_RCVBUF = 128 * 1024 * 1024,
42
43 // Might be made smaller: the kernel v5.4 passes up to 32 environment
44 // variables with a total of 2kb on each event.
45 // On top of that the action string and device path are added.
46 USER_RCVBUF = 16 * 1024,
38}; 47};
39 48
40#ifndef SO_RCVBUFFORCE
41#define SO_RCVBUFFORCE 33
42#endif
43enum { RCVBUF = 2 * 1024 * 1024 };
44
45int uevent_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; 49int uevent_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
46int uevent_main(int argc UNUSED_PARAM, char **argv) 50int uevent_main(int argc UNUSED_PARAM, char **argv)
47{ 51{
@@ -57,7 +61,8 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
57 // Reproducer: 61 // Reproducer:
58 // uevent mdev & 62 // uevent mdev &
59 // find /sys -name uevent -exec sh -c 'echo add >"{}"' ';' 63 // find /sys -name uevent -exec sh -c 'echo add >"{}"' ';'
60 fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, /*groups:*/ 1 << 0, RCVBUF); 64 reopen:
65 fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, /*groups:*/ 1 << 0, KERN_RCVBUF);
61 66
62 for (;;) { 67 for (;;) {
63 char *netbuf; 68 char *netbuf;
@@ -69,17 +74,20 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
69 // for a new uevent notification to come in. 74 // for a new uevent notification to come in.
70 // We use a fresh mmap so that buffer is not allocated 75 // We use a fresh mmap so that buffer is not allocated
71 // until kernel actually starts filling it. 76 // until kernel actually starts filling it.
72 netbuf = mmap(NULL, BUFFER_SIZE, 77 netbuf = xmmap_anon(USER_RCVBUF);
73 PROT_READ | PROT_WRITE,
74 MAP_PRIVATE | MAP_ANON,
75 /* ignored: */ -1, 0);
76 if (netbuf == MAP_FAILED)
77 bb_simple_perror_msg_and_die("mmap");
78 78
79 // Here we block, possibly for a very long time 79 // Here we block, possibly for a very long time
80 len = safe_read(fd, netbuf, BUFFER_SIZE - 1); 80 len = safe_read(fd, netbuf, USER_RCVBUF - 1);
81 if (len < 0) 81 if (len < 0) {
82 if (errno == ENOBUFS) {
83 // Ran out of socket receive buffer
84 bb_simple_error_msg("uevent overrun");
85 close(fd);
86 munmap(netbuf, USER_RCVBUF);
87 goto reopen;
88 }
82 bb_simple_perror_msg_and_die("read"); 89 bb_simple_perror_msg_and_die("read");
90 }
83 end = netbuf + len; 91 end = netbuf + len;
84 *end = '\0'; 92 *end = '\0';
85 93
@@ -108,7 +116,7 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
108 while (env[idx]) 116 while (env[idx])
109 bb_unsetenv(env[idx++]); 117 bb_unsetenv(env[idx++]);
110 } 118 }
111 munmap(netbuf, BUFFER_SIZE); 119 munmap(netbuf, USER_RCVBUF);
112 } 120 }
113 121
114 return 0; // not reached 122 return 0; // not reached