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Bug #44218 Misdirected output after closing stdout/stderr and working with files.
Submitted: 2008-02-22 17:58 UTC Modified: 2008-02-24 00:35 UTC
From: exe at travian dot org Assigned:
Status: Not a bug Package: Filesystem function related
PHP Version: 5.2.5 OS: GNU/Linux Kernel 2.6.18
Private report: No CVE-ID: None
 [2008-02-22 17:58 UTC] exe at travian dot org
Description:
------------
If STDOUT/STDERR are closed by a script then the first two file handles opened by that script afterwards will take the place of the former STDOUT/STDERR handles. This will cause any output which normaly goes to STDOUT (like in print/echo statements) to be written to the new file handles. This behaviour may corrupt files written by that script.

This is a similar problem as in bug #44217.

Reproduce code:
---------------
<?php
fclose(STDOUT); fclose(STDERR);

$fp1 = fopen('test.log', 'a'); // File handle 1, formerly STDOUT
$fp2 = fopen('test.log', 'a'); // File handle 2, formerly STDERR

print "foo"; // Will be written to test.log
?>

Expected result:
----------------
No output from php, no appended output in test.log

Actual result:
--------------
String "foo" will be appended to test.log

strace shows that php first closes file handle 1 (stdout) and 2 (stderr) and then openes two file handles, which get the numbers 1 and 2, and then print "foo" to file handle 1 which now points to test.log:

read(3, "<?php\nfclose(STDOUT); fclose(STD"..., 8192) = 217
read(3, "", 4096)                       = 0
read(3, "", 8192)                       = 0
close(3)                                = 0
munmap(0x2b97a043e000, 4096)            = 0
close(1)                                = 0
munmap(0x2b97a0440000, 4096)            = 0
close(2)                                = 0
getcwd("/root", 4096)                   = 6
lstat("/root", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/root/test.log", {st_mode=S_IFREG|0644, st_size=290, ...}) = 0
open("/root/test.log", O_WRONLY|O_APPEND|O_CREAT, 0666) = 1
fstat(1, {st_mode=S_IFREG|0644, st_size=290, ...}) = 0
lseek(1, 0, SEEK_CUR)                   = 0
lseek(1, 0, SEEK_CUR)                   = 0
getcwd("/root", 4096)                   = 6
open("/root/test.log", O_WRONLY|O_APPEND|O_CREAT, 0666) = 2
fstat(2, {st_mode=S_IFREG|0644, st_size=290, ...}) = 0
lseek(2, 0, SEEK_CUR)                   = 0
lseek(2, 0, SEEK_CUR)                   = 0
write(1, "foo", 3)                      = 3
close(2)                                = 0
close(1)                                = 0
close(0)                                = 0
munmap(0x2b97a043f000, 4096)            = 0
munmap(0x2b97a03fd000, 266240)          = 0
mmap(NULL, 266240, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2b97a03fd000
setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0
munmap(0x2b97a03fd000, 266240)          = 0
brk(0xd36000)                           = 0xd36000
exit_group(0)                           = ?
Process 19229 detached



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 [2008-02-24 00:35 UTC] jani@php.net
This is same issue. One report per problem.
 
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