linuxolator problem on i386

[Boris Samorodov]

Hi!


I like magic numbers. Ex. 4096. ;-)
And I like to play with them.


On Tue, 18 Sep 2007 12:38:28 +0400 Boris Samorodov wrote:

> > 2) when the directory is moved it works ok
> Yes. And I suppose if some files are deletted the program should
> work.

It so happened that here we get a deal with magic (number). Let me
show you the broken behaviour one more time:
-----
 14594 hlds_i686 NAMI  "/usr/home/bsam/hlds_l/./cstrike/sound/weapons"
 14594 hlds_i686 RET   linux_open 6
 14594 hlds_i686 CALL  linux_fstat64(0x6,0xbfbecd34,0x2820cff4)
 14594 hlds_i686 RET   linux_fstat64 0
 14594 hlds_i686 CALL  linux_fcntl64(0x6,0x2,0x1)
 14594 hlds_i686 RET   linux_fcntl64 0
 14594 hlds_i686 CALL  linux_getdents(0x6,0x8da5b44,0x1000)
 14594 hlds_i686 RET   linux_getdents 4096/0x1000
 14594 hlds_i686 CALL  linux_getdents(0x6,0x8da5b44,0x1000)
 14594 hlds_i686 RET   linux_getdents 444/0x1bc
 14594 hlds_i686 CALL  linux_getdents(0x6,0x8da5b44,0x1000)
 14594 hlds_i686 RET   linux_getdents 0
 14594 hlds_i686 CALL  linux_open(0x281e0fc7,0x902,0)
 14594 hlds_i686 NAMI  "/compat/linux/dev/tty"
 14594 hlds_i686 NAMI  "/dev/tty"
 14594 hlds_i686 RET   linux_open 7
 14595 hlds_i686 CALL  linux_sys_futex(0x2820e120,0,0x2,0,0x8da5720,0x2f45b0f8)
 14594 hlds_i686 CALL  writev(0x7,0xbfbec6b0,0x7)
 14594 hlds_i686 GIO   fd 7 wrote 86 bytes
       "*** glibc detected *** ./hlds_i686: double free or corruption (!prev):\
         0x08da5b28 ***
       "
-----

Look at the first linux_getdents() line. The third parameter (buffer
length?) equals to 0x1000 which is 4096. The second line with
linux_getdents shows that it has read precisely 4096 (bytes?). What if
we face here a (so called at our high school) border-case
(border-problem)?

OK, the program reads the directory contents. Lets touch a new file
at this directory. What does happen? Follow me:
-----
 14579 hlds_i686 NAMI  "/usr/home/bsam/hlds_l/./cstrike/sound/weapons"
 14579 hlds_i686 RET   linux_open 6
 14579 hlds_i686 CALL  linux_fstat64(0x6,0xbfbecd34,0x2820cff4)
 14579 hlds_i686 RET   linux_fstat64 0
 14579 hlds_i686 CALL  linux_fcntl64(0x6,0x2,0x1)
 14579 hlds_i686 RET   linux_fcntl64 0
 14579 hlds_i686 CALL  linux_getdents(0x6,0x8da574c,0x1000)
 14579 hlds_i686 RET   linux_getdents 4084/0xff4
 14579 hlds_i686 CALL  linux_getdents(0x6,0x8da574c,0x1000)
 14579 hlds_i686 RET   linux_getdents 472/0x1d8
 14579 hlds_i686 CALL  linux_getdents(0x6,0x8da574c,0x1000)
 14579 hlds_i686 RET   linux_getdents 0
 14579 hlds_i686 CALL  close(0x6)
 14579 hlds_i686 RET   close 0
 14579 hlds_i686 CALL  linux_stat64(0xbfbecec4,0xbfbecdc4,0x2820cff4)
 14579 hlds_i686 NAMI  "/compat/linux/usr/home/bsam/hlds_l/./valve/sound/weapons/reload1.wav"
-----

That's it! <loud long applauses>

Roman, I hope now you may create the needed patch.
As for me I'm too tied (and too proud :-) ) today and 'm going to have
a little sleep.


WBR and good night to all ya!
-- 
Boris Samorodov (bsam)
Research Engineer, http://www.ipt.ru Telephone & Internet SP
FreeBSD committer, http://www.FreeBSD.org The Power To Serve