How to find a bug: is_link troubles

Brian Moon wrote:

Works fine under Apache1. I don't have Apache2 handy on this box. But I can't see this being affected by the SAPI in any way other than user permissions and/or some sort of SELinux restriction. As in, things external to PHP itself. So, if someone who knows their way around strace can reproduce this problem and show me the series of syscalls and their exit status, we can probably figure out what is happening. I'm about 90% sure this is not a PHP problem, but rather a system configuration problem. -Rasmus

Miscopied, a full strace is: lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat64("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 access("/tmp/pear", F_OK) = 0 time(NULL) = 1179959483 lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat64("/tmp/link-test", {st_mode=S_IFLNK|0777, st_size=9, ...}) = 0 readlink("/tmp/link-test", "/tmp/pear", 4096) = 9 lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat64("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 access("/tmp/pear", F_OK) = 0 unlink("/tmp/link-test") = 0 time(NULL) = 1179959483 lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat64("/tmp/link-test", 0xbff2137c) = -1 ENOENT (No such file or directory) time(NULL) = 1179959483 lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat64("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 symlink("/tmp/pear", "/tmp/link-test") = 0 time(NULL) = 1179959483 lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat64("/tmp/link-test", {st_mode=S_IFLNK|0777, st_size=9, ...}) = 0 readlink("/tmp/link-test", "/tmp/pear", 4096) = 9 lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat64("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 lstat64("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 write(1, "dir", 3dir) = 3 write(1, "\n", 1 ) = 1 write(1, "not a link", 10not a link) = 10 write(1, "\n", 1 ) = 1 time(NULL) = 1179959483 lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat64("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 stat64("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 write(1, "same", 4same) = 4 SELinux is disabled on the box. Scott Rasmus Lerdorf wrote:

Works as expected on my Mac (no strace on my Mac). On my Gentoo 64-bit server, I get the wrong data from Apache2 and CLI. On my 32-bit Gentoo server, without Apache 2, I get the correct answer from apache and cli. On my 32-bit Gentoo server with Apache 2 I get a wrong answer from Apache and cli. We build our PHP on these servers with the same options via emerge. The only difference is Apache 2. What the hell? # uname -a Linux proxy1 2.6.18-gentoo-r6 #1 SMP Thu Feb 8 07:32:31 EST 2007 x86_64 Dual-Core AMD Opteron(tm) Processor 2210 AuthenticAMD GNU/Linux # php foobar.php dir not a link same lstat("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 access("/tmp/pear", F_OK) = 0 lstat("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat("/tmp/link-test", {st_mode=S_IFLNK|0777, st_size=9, ...}) = 0 readlink("/tmp/link-test", "/tmp/pear", 4096) = 9 lstat("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 access("/tmp/pear", F_OK) = 0 unlink("/tmp/link-test") = 0 lstat("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat("/tmp/link-test", 0x7fff3f48fb70) = -1 ENOENT (No such file or directory) lstat("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 symlink("/tmp/pear", "/tmp/link-test") = 0 lstat("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat("/tmp/link-test", {st_mode=S_IFLNK|0777, st_size=9, ...}) = 0 readlink("/tmp/link-test", "/tmp/pear", 4096) = 9 lstat("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 lstat("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2b906b634000 write(1, "dir", 3dir) = 3 write(1, "\n", 1 ) = 1 write(1, "not a link", 10not a link) = 10 write(1, "\n", 1 ) = 1 lstat("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=4096, ...}) = 0 lstat("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 stat("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 write(1, "same", 4same) = 4 32-bit Gentoo however acts as expected. $ uname -a Linux deadpool 2.6.11-gentoo-r6 #1 SMP Thu Apr 14 07:52:09 EDT 2005 i686 Intel(R) Xeon(TM) CPU 3.20GHz GenuineIntel GNU/Linux php test.php link link differ access("/tmp/pear", F_OK) = 0 access("/tmp/link-test", F_OK) = 0 unlink("/tmp/link-test") = 0 time(NULL) = 1179959743 lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=14416, ...}) = 0 lstat64("/tmp/link-test", 0xbfff5e4c) = -1 ENOENT (No such file or directory) time(NULL) = 1179959743 lstat64("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=14416, ...}) = 0 lstat64("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=72, ...}) = 0 symlink("/tmp/pear", "/tmp/link-test") = 0 lstat64("/tmp/link-test", {st_mode=S_IFLNK|0777, st_size=9, ...}) = 0 fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb78b1000 write(1, "link", 4link) = 4 write(1, "\n", 1 ) = 1 write(1, "link", 4link) = 4 write(1, "\n", 1 ) = 1 stat64("/tmp/pear", {st_mode=S_IFDIR|0755, st_size=72, ...}) = 0 write(1, "differ", 6differ) = 6 Rasmus Lerdorf wrote: