libudev: monitor - use simpler hash

3 files changed, 36 insertions, 80 deletions

diff --git a/udev/lib/libudev-monitor.c b/udev/lib/libudev-monitor.c
index 570fcafbb4..a0f93546f7 100644
--- a/udev/lib/libudev-monitor.c
+++ b/udev/lib/libudev-monitor.c
@@ -56,8 +56,9 @@ struct udev_monitor_netlink_header {
 	unsigned short properties_off;
 	unsigned short properties_len;
 	/*
-	 * crc32 of some common device properties to filter with socket filters in the client
-	 * used in the kernel from socket filter rules; needs to be stored in network order
+	 * hashes of some common device propertie strings to filter with socket filters in
+	 * the client used in the kernel from socket filter rules; needs to be stored in
+	 * network order
 	 */
 	unsigned int filter_subsystem;
 };
@@ -247,11 +248,11 @@ static int filter_apply(struct udev_monitor *udev_monitor)
 	/* add all subsystem match values */
 	udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_subsystem_list)) {
 		const char *subsys = udev_list_entry_get_name(list_entry);
-		unsigned int crc;
+		unsigned int hash;
 
-		crc = util_crc32((unsigned char *)subsys, strlen(subsys));
+		hash = util_string_hash32(subsys);
 		/* jump if value does not match */
-		bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, crc, 0, 1);
+		bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
 		/* matched, pass packet */
 		bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
 
@@ -414,8 +415,9 @@ struct udev_device *udev_monitor_receive_device(struct udev_monitor *udev_monito
 	struct cmsghdr *cmsg;
 	struct sockaddr_nl snl;
 	struct ucred *cred;
-	char buf[4096];
-	size_t bufpos;
+	char buf[8192];
+	ssize_t buflen;
+	ssize_t bufpos;
 	struct udev_monitor_netlink_header *nlh;
 	int devpath_set = 0;
 	int subsystem_set = 0;
@@ -440,12 +442,18 @@ retry:
 		smsg.msg_namelen = sizeof(snl);
 	}
 
-	if (recvmsg(udev_monitor->sock, &smsg, 0) < 0) {
+	buflen = recvmsg(udev_monitor->sock, &smsg, 0);
+	if (buflen < 0) {
 		if (errno != EINTR)
 			info(udev_monitor->udev, "unable to receive message\n");
 		return NULL;
 	}
 
+	if (buflen < 32 || (size_t)buflen >= sizeof(buf)) {
+		info(udev_monitor->udev, "invalid message length\n");
+		return NULL;
+	}
+
 	if (udev_monitor->snl.nl_family != 0) {
 		if (snl.nl_groups == 0) {
 			info(udev_monitor->udev, "unicast netlink message ignored\n");
@@ -469,18 +477,20 @@ retry:
 		return NULL;
 	}
 
-	nlh = (struct udev_monitor_netlink_header *) buf;
-	if (nlh->magic == ntohl(UDEV_MONITOR_MAGIC)) {
-		/* udev message with version magic */
+	if (strncmp(buf, "udev-", 5) == 0) {
+		/* udev message needs proper version magic */
+		nlh = (struct udev_monitor_netlink_header *) buf;
+		if (nlh->magic != htonl(UDEV_MONITOR_MAGIC))
+			return NULL;
 		if (nlh->properties_off < sizeof(struct udev_monitor_netlink_header))
 			return NULL;
-		if (nlh->properties_off+32U > sizeof(buf))
+		if (nlh->properties_off+32U > buflen)
 			return NULL;
 		bufpos = nlh->properties_off;
 	} else {
 		/* kernel message with header */
 		bufpos = strlen(buf) + 1;
-		if (bufpos < sizeof("a@/d") || bufpos >= sizeof(buf)) {
+		if ((size_t)bufpos < sizeof("a@/d") || bufpos >= buflen) {
 			info(udev_monitor->udev, "invalid message length\n");
 			return NULL;
 		}
@@ -497,7 +507,7 @@ retry:
 		return NULL;
 	}
 
-	while (bufpos < sizeof(buf)) {
+	while (bufpos < buflen) {
 		char *key;
 		size_t keylen;
 
@@ -629,7 +639,6 @@ int udev_monitor_send_device(struct udev_monitor *udev_monitor, struct udev_devi
 		smsg.msg_namelen = udev_monitor->addrlen;
 	} else if (udev_monitor->snl.nl_family != 0) {
 		const char *val;
-		size_t vlen;
 		struct udev_monitor_netlink_header nlh;
 
 
@@ -638,8 +647,7 @@ int udev_monitor_send_device(struct udev_monitor *udev_monitor, struct udev_devi
 		util_strlcpy(nlh.version, "udev-" VERSION, sizeof(nlh.version));
 		nlh.magic = htonl(UDEV_MONITOR_MAGIC);
 		val = udev_device_get_subsystem(udev_device);
-		vlen = strlen(val);
-		nlh.filter_subsystem = htonl(util_crc32((unsigned char *)val, vlen));
+		nlh.filter_subsystem = htonl(util_string_hash32(val));
 		iov[0].iov_base = &nlh;
 		iov[0].iov_len = sizeof(struct udev_monitor_netlink_header);
 
diff --git a/udev/lib/libudev-private.h b/udev/lib/libudev-private.h
index 178004c485..0756efea81 100644
--- a/udev/lib/libudev-private.h
+++ b/udev/lib/libudev-private.h
@@ -173,5 +173,5 @@ extern int udev_util_replace_whitespace(const char *str, char *to, size_t len);
 extern int udev_util_replace_chars(char *str, const char *white);
 extern int udev_util_encode_string(const char *str, char *str_enc, size_t len);
 extern void util_set_fd_cloexec(int fd);
-extern unsigned int util_crc32(const unsigned char *buf, size_t len);
+extern unsigned int util_string_hash32(const char *str);
 #endif
diff --git a/udev/lib/libudev-util.c b/udev/lib/libudev-util.c
index 018e2cdb08..2b8cda59f6 100644
--- a/udev/lib/libudev-util.c
+++ b/udev/lib/libudev-util.c
@@ -462,67 +462,15 @@ void util_set_fd_cloexec(int fd)
 	fcntl(fd, F_SETFD, flags);
 }
 
-unsigned int util_crc32(const unsigned char *buf, size_t len)
+unsigned int util_string_hash32(const char *str)
 {
-	unsigned int crc;
-	const unsigned char *end;
-	static const unsigned int crc32_table[256] = {
-		0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
-		0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
-		0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
-		0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
-		0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
-		0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
-		0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
-		0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
-		0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
-		0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
-		0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
-		0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
-		0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
-		0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
-		0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
-		0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
-		0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
-		0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
-		0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
-		0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
-		0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
-		0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
-		0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
-		0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
-		0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
-		0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
-		0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
-		0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
-		0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
-		0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
-		0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
-		0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
-		0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
-		0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
-		0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
-		0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
-		0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
-		0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
-		0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
-		0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
-		0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
-		0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
-		0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
-		0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
-		0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
-		0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
-		0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
-		0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
-		0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
-		0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
-		0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
-		0x2d02ef8d
-	};
-
-	crc = 0xffffffff;
-	for (end = buf + len; buf < end; ++buf)
-		crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
-	return ~crc;
+	unsigned int hash = 0;
+
+	while (str[0] != '\0') {
+		hash += str[0] << 4;
+		hash += str[0] >> 4;
+		hash *= 11;
+		str++;
+	}
+	return hash;
 }