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httpd: treat errors from stdin correctly.

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Fron bug report:

If a CGI or proxied connection is rudely aborted (SIG_{KILL,BUS,SEGV})
then httpd will spin madly the poll loop in:

networking/httpd.c:1080
cgi_io_loop_and_exit()

Upon investigation I found that pfd[0].revents == 0x0018 (POLLHUP|POLLERR),
which leads to empty read, but the pfd[0].fd (STDIN_FILENO) is left open,
and in the FD list given to poll() which immediately returns to once
again inform the loop of (POLLHUP|POLLERR) condition of pfd[0].fd.
This continues until pfd[FROM_CGI].revents != 0

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2013-09-11 14:59:21 +02:00
parent b5352078a7
commit fbe250db76
1 changed files with 13 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
networking/httpd.c
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@ -1105,16 +1105,21 @@ static NOINLINE void cgi_io_loop_and_exit(int fromCgi_rd, int toCgi_wr, int post
/* NB: breaking out of this loop jumps to log_and_exit() */
out_cnt = 0;
while (1) {
memset(pfd, 0, sizeof(pfd));
/* Note: even pfd[0].events == 0 won't prevent
* revents == POLLHUP|POLLERR reports from closed stdin.
* This works: */
pfd[0].fd = -1;
pfd[FROM_CGI].fd = fromCgi_rd;
pfd[FROM_CGI].events = POLLIN;
if (toCgi_wr) {
pfd[TO_CGI].fd = toCgi_wr;
if (hdr_cnt > 0) {
pfd[TO_CGI].events = POLLOUT;
} else if (post_len > 0) {
if (toCgi_wr && hdr_cnt <= 0) {
if (post_len > 0) {
/* Expect more POST data from network */
pfd[0].fd = 0;
pfd[0].events = POLLIN;
} else {
/* post_len <= 0 && hdr_cnt <= 0:
@ -1127,7 +1132,7 @@ static NOINLINE void cgi_io_loop_and_exit(int fromCgi_rd, int toCgi_wr, int post
}
/* Now wait on the set of sockets */
count = safe_poll(pfd, toCgi_wr ? TO_CGI+1 : FROM_CGI+1, -1);
count = safe_poll(pfd, hdr_cnt > 0 ? TO_CGI+1 : FROM_CGI+1, -1);
if (count <= 0) {
#if 0
if (safe_waitpid(pid, &status, WNOHANG) <= 0) {
@ -1144,7 +1149,7 @@ static NOINLINE void cgi_io_loop_and_exit(int fromCgi_rd, int toCgi_wr, int post
}
if (pfd[TO_CGI].revents) {
/* hdr_cnt > 0 here due to the way pfd[TO_CGI].events set */
/* hdr_cnt > 0 here due to the way poll() called */
/* Have data from peer and can write to CGI */
count = safe_write(toCgi_wr, hdr_ptr, hdr_cnt);
/* Doesn't happen, we dont use nonblocking IO here