general/6254: Reason for failed fopen not checked in default_handler

[Erik Agsj� <er...@aktiedirekt.com>]

>Number:         6254
>Category:       general
>Synopsis:       Reason for failed fopen not checked in default_handler
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    apache
>State:          open
>Class:          sw-bug
>Submitter-Id:   apache
>Arrival-Date:   Thu Jun 29 03:30:02 PDT 2000
>Closed-Date:
>Last-Modified:
>Originator:     erik.agsjo@aktiedirekt.com
>Release:        1.3.12
>Organization:
apache
>Environment:
Development:
SunOS plumpen 5.6 Generic_105181-11 sun4m sparc SUNW,SPARCstation-10
gcc version 2.95.2 19991024 (release)

Production:
SunOS molly 5.6 Generic_105181-17 sun4u sparc SUNW,UltraSPARC-IIi-cEngine

Apache setup:

# ./httpd -l
Compiled-in modules:
  http_core.c
  mod_env.c
  mod_log_config.c
  mod_mime.c
  mod_status.c
  mod_include.c
  mod_dir.c
  mod_actions.c
  mod_alias.c
  mod_access.c
  mod_auth.c
  mod_proxy.c
  mod_setenvif.c
  mod_ssl.c
  mod_jserv.c
  mod_cookieauth.c
  mod_error.c

# ./httpd -V
Server version: Apache/1.3.12 (Unix)
Server built:   Jun 28 2000 13:34:33
Server's Module Magic Number: 19990320:7
Server compiled with....
 -D EAPI
 -D EAPI_MM
 -D EAPI_MM_CORE_PATH="logs/httpd.mm"
 -D HAVE_MMAP
 -D USE_MMAP_SCOREBOARD
 -D USE_MMAP_FILES
 -D USE_FCNTL_SERIALIZED_ACCEPT
 -D HTTPD_ROOT="/usr/local/apache"
 -D SUEXEC_BIN="/usr/local/apache/bin/suexec"
 -D DEFAULT_PIDLOG="logs/httpd.pid"
 -D DEFAULT_SCOREBOARD="logs/httpd.scoreboard"
 -D DEFAULT_LOCKFILE="logs/httpd.lock"
 -D DEFAULT_XFERLOG="logs/access_log"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D TYPES_CONFIG_FILE="conf/mime.types"
 -D SERVER_CONFIG_FILE="conf/httpd.conf"
 -D ACCESS_CONFIG_FILE="conf/access.conf"
 -D RESOURCE_CONFIG_FILE="conf/srm.conf"

The error and cookieauth modules are internally developed modules at our site.
>Description:
Our servers experience strange problems after they have been running for a while.
Random accesses get "file permissions deny server access" errors while other accesses to the same file work prefectly.
In our efforts to find the problem we added the child process pid to the error logs, but the problem seamed to appear on all children.

While looking at the code we realized that the default handler assumes that a failed fopen is because of file permission problems.
This is not the case for us, as the following patch showed.
The reason for the failed fopen is still a mystery, since errno is set to 0.
>How-To-Repeat:
Well, if you can think up a situation where fopen would fail while file permissions allow access, you would see the erroneous "file permissions deny server access".
>Fix:
Here is a patch with a suggested fix for checking errno on failed fopen.
A workaround for our real problem is to set maxrequests to 100 or something until someone comes up with a solution.

---------------------------------------------------------

*** http_core.old       Fri Feb 18 21:41:47 2000
--- http_core.c Wed Jun 28 13:34:09 2000
***************
*** 3108,3116 ****
  #endif
  
      if (f == NULL) {
!         ap_log_rerror(APLOG_MARK, APLOG_ERR, r,
!                    "file permissions deny server access: %s", r->filename);
!         return FORBIDDEN;
      }
        
      ap_update_mtime(r, r->finfo.st_mtime);
--- 3108,3126 ----
  #endif
  
      if (f == NULL) {
!       if (errno == EACCES) {
!           ap_log_rerror(APLOG_MARK, APLOG_ERR, r,
!                         "file permissions deny server access: %s",
!                         r->filename);
!           return FORBIDDEN;
!       }
!       else {
!           ap_log_rerror(APLOG_MARK, APLOG_ERR, r,
!                         "file open error: %s, OS error: %s",
!                         r->filename,
!                         strerror(errno));
!           return SERVER_ERROR;
!       }
      }
        
      ap_update_mtime(r, r->finfo.st_mtime);

---------------------------------------------------------
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