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curl_multi_fdset: avoid FD_SET out of bounds

If a socket is larger than FD_SETSIZE, avoid using FD_SET() on the
platforms where this is possible.

Bug: http://curl.haxx.se/bug/view.cgi?id=3413274
Reported by: Tim Starling
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1 parent bb94b92 commit 2d6796aac51d8a5963f552b8fa23a2396a987913 @bagder bagder committed Sep 25, 2011
Showing with 27 additions and 16 deletions.
  1. +8 −0 docs/libcurl/curl_multi_fdset.3
  2. +3 −2 lib/multi.c
  3. +0 −14 lib/select.c
  4. +16 −0 lib/select.h
@@ -53,6 +53,14 @@ When doing select(), you should use \fBcurl_multi_timeout\fP to figure out how
long to wait for action. Call \fIcurl_multi_perform\fP even if no activity has
been seen on the fd_sets after the timeout expires as otherwise internal
retries and timeouts may not work as you'd think and want.
+
+If one of the sockets used by libcurl happens to be larger than what can be
+set in an fd_set, which on POSIX systems means that the file descriptor is
+larger than FD_SETSIZE, then libcurl will try to not set it. Setting a too
+large file descriptor in an fd_set implies an out of bounds write which can
+cause crashes, or worse. The effect of NOT storing it will possibly save you
+from the crash, but will make your program NOT wait for sockets it should wait
+for...
.SH RETURN VALUE
CURLMcode type, general libcurl multi interface error code. See
\fIlibcurl-errors(3)\fP
View
@@ -42,6 +42,7 @@
#include "timeval.h"
#include "http.h"
#include "warnless.h"
+#include "select.h"
#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>
@@ -907,11 +908,11 @@ CURLMcode curl_multi_fdset(CURLM *multi_handle,
for(i=0; i< MAX_SOCKSPEREASYHANDLE; i++) {
curl_socket_t s = CURL_SOCKET_BAD;
- if(bitmap & GETSOCK_READSOCK(i)) {
+ if((bitmap & GETSOCK_READSOCK(i)) && VALID_SOCK((sockbunch[i]))) {
FD_SET(sockbunch[i], read_fd_set);
s = sockbunch[i];
}
- if(bitmap & GETSOCK_WRITESOCK(i)) {
+ if((bitmap & GETSOCK_WRITESOCK(i)) && VALID_SOCK((sockbunch[i]))) {
FD_SET(sockbunch[i], write_fd_set);
s = sockbunch[i];
}
View
@@ -46,20 +46,6 @@
#include "select.h"
#include "warnless.h"
-/* Winsock and TPF sockets are not in range [0..FD_SETSIZE-1] */
-
-#if defined(USE_WINSOCK) || defined(TPF)
-#define VERIFY_SOCK(x) Curl_nop_stmt
-#else
-#define VALID_SOCK(s) (((s) >= 0) && ((s) < FD_SETSIZE))
-#define VERIFY_SOCK(x) do { \
- if(!VALID_SOCK(x)) { \
- SET_SOCKERRNO(EINVAL); \
- return -1; \
- } \
-} WHILE_FALSE
-#endif
-
/* Convenience local macros */
#define elapsed_ms (int)curlx_tvdiff(curlx_tvnow(), initial_tv)
View
@@ -96,4 +96,20 @@ int tpf_select_libcurl(int maxfds, fd_set* reads, fd_set* writes,
fd_set* excepts, struct timeval* tv);
#endif
+/* Winsock and TPF sockets are not in range [0..FD_SETSIZE-1], which
+ unfortunately makes it impossible for us to easily check if they're valid
+*/
+#if defined(USE_WINSOCK) || defined(TPF)
+#define VALID_SOCK(x) 1
+#define VERIFY_SOCK(x) Curl_nop_stmt
+#else
+#define VALID_SOCK(s) (((s) >= 0) && ((s) < FD_SETSIZE))
+#define VERIFY_SOCK(x) do { \
+ if(!VALID_SOCK(x)) { \
+ SET_SOCKERRNO(EINVAL); \
+ return -1; \
+ } \
+} WHILE_FALSE
+#endif
+
#endif /* __SELECT_H */

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