sin/samba-mirror
1
0
Fork 0
mirror of https://github.com/samba-team/samba.git synced 2025-03-02 08:58:33 +03:00
Code

Fix an invalid typecasting

Browse Source 
entry->num_of_strings is a uint16_t. Casting it with

(int *)&entry->num_of_strings

is wrong, because it gives add_string_to_array the illusion that the object
"num" points to is an int, which it is not.

In case we are running on a machine where "int" is 32 or 64 bits long, what
happens with that cast? "add_string_to_array" interprets the byte field that
starts where "num_of_strings" starts as an int. Under very particular
circumstances this might work in a limited number of cases: When the byte order
of an int is such that the lower order bits of the int are stored first, the
subsequent bytes which do not belong to the uint16_t anymore happen to be 0 and
the result of the increment still fits into the first 2 bytes of that int, i.e.
the result is < 65536.

The correct solution to this problem is to use the implicit type conversion
that happens when an assignment is done.

BTW, this bug is found if you compile with -O3 -Wall, it shows up as a warning:

rpc_server/srv_eventlog_lib.c:574: warning: dereferencing type-punned pointer
	will break strict-aliasing rules

Thanks,

Volker
This commit is contained in:
Volker Lendecke 2009-02-14 18:01:20 +01:00 committed by Günther Deschner
parent 612c5e746b
commit ea192f08e6
1 changed files with 7 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
source3/rpc_server/srv_eventlog_lib.c
View File

@ -560,6 +560,7 @@ bool parse_logentry( TALLOC_CTX *mem_ctx, char *line, struct eventlog_Record_tdb
}
} else if ( 0 == strncmp( start, "STR", stop - start ) ) {
size_t tmp_len;
int num_of_strings;
/* skip past initial ":" */
stop++;
/* now skip any other leading whitespace */
@ -570,10 +571,15 @@ bool parse_logentry( TALLOC_CTX *mem_ctx, char *line, struct eventlog_Record_tdb
if (tmp_len == (size_t)-1) {
return false;
}
num_of_strings = entry->num_of_strings;
if (!add_string_to_array(mem_ctx, stop, &entry->strings,
(int *)&entry->num_of_strings)) {
&num_of_strings)) {
return false;
}
if (num_of_strings > 0xffff) {
return false;
}
entry->num_of_strings = num_of_strings;
entry->strings_len += tmp_len;
} else if ( 0 == strncmp( start, "DAT", stop - start ) ) {
/* skip past initial ":" */