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socket-util: Let's trick out ubsan when it validate struct sockaddr_un.sun_path[]

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Linux is stupid and sometimes returns a "struct sockaddr_un" that is
longer than its fields, as it NUL terminates .sun_path[] even if it has
full length. ubsan detects this, rightfully. Since this is a Linux
misdesign let's trick out ubsan a bit.

Fixes: #11024
This commit is contained in:
Lennart Poettering 2018-12-04 18:21:25 +01:00
parent 836f9cfebd
commit 085b39e9df
1 changed files with 9 additions and 4 deletions
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13
src/basic/socket-util.c
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@ -661,9 +661,14 @@ int sockaddr_pretty(
/* The name must have at least one character (and the leading NUL does not count) */
p = strdup("<unnamed>");
else {
/* Note that we calculate the path pointer here through the .un_buffer[] field, in order to
* outtrick bounds checking tools such as ubsan, which are too smart for their own good: on
* Linux the kernel may return sun_path[] data one byte longer than the declared size of the
* field. */
char *path = (char*) sa->un_buffer + offsetof(struct sockaddr_un, sun_path);
size_t path_len = salen - offsetof(struct sockaddr_un, sun_path);
if (sa->un.sun_path[0] == 0) {
if (path[0] == 0) {
/* Abstract socket. When parsing address information from, we
* explicitly reject overly long paths and paths with embedded NULs.
* But we might get such a socket from the outside. Let's return
@ -671,17 +676,17 @@ int sockaddr_pretty(
_cleanup_free_ char *e = NULL;
e = cescape_length(sa->un.sun_path + 1, path_len - 1);
e = cescape_length(path + 1, path_len - 1);
if (!e)
return -ENOMEM;
p = strjoin("@", e);
} else {
if (sa->un.sun_path[path_len - 1] == '\0')
if (path[path_len - 1] == '\0')
/* We expect a terminating NUL and don't print it */
path_len --;
p = cescape_length(sa->un.sun_path, path_len);
p = cescape_length(path, path_len);
}
}
if (!p)