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Re: cfservd - Segfaults Almost Solved


From: Mark . Burgess
Subject: Re: cfservd - Segfaults Almost Solved
Date: Thu, 8 Apr 2004 11:07:27 +0200 (MEST)

Thanks for this information. The correct resolution to this problem
is to test whether last is NULL.

The double free has been found and fixed.
I enclose a patched item-ext to 2.1.4  for convenience,

Do let me know whether this solves your problem with segfaulting.
thanks!

Mark

On  7 Apr, Ned Ludd wrote:
> Lance, Kurt.
> 
> It looks like 'last' is NULL on line 709 last->next = ip->next; I would
> assume (not checked) that the code is supposed to have a last = (some
> type) malloc(sizeof(last/last[0])) thing going on elsewhere. I think
> this is the reason for the consonant segfaults. Some other debugging
> appears to also show it to be a double free, but I don't have that debug
> info handy. Anyway I have included what I think should be enough info
> for the author to take a closer look and hopefully release an updated
> version.  If additional debugging information or a core file is needed
> they can be provided upon request.
> 
> eagle root # uname -a
> Linux eagle 2.4.23-grsec-1.9.13 #1 Mon Dec 1 22:35:09 UTC 2003 i686
> Pentium III (Coppermine) GenuineIntel GNU/Linux
> 
> eagle root # file `which cfservd`
> /usr/sbin/cfservd: ELF 32-bit LSB executable, Intel 80386, version 1
> (SYSV), for GNU/Linux 2.4.1, dynamically linked (uses shared libs), not
> stripped
> 
> eagle root # gcc --version
> gcc (GCC) 3.3.2 20031218 (Gentoo Linux 3.3.2-r5, propolice-3.3-7)
> 
> eagle root # ld -v
> GNU ld version 2.14.90.0.7 20031029
> 
> glibc-2.3.2-r9  without nls, nptl 
> 
> cfengine-2.1.3
> 
> ------------------------------------------------------------------------
> strace output
> ------------------------------------------------------------------------
> 
> [26b73211] select(6, [5], NULL, NULL, NULL) = 1 (in [5])
> [26a35a58] accept(5, {sin_family=AF_INET, sin_port=htons(54682),
> sin_addr=inet_addr("204.225.92.140")}}, [16]) = 3
> [26b344cd] time(NULL)                   = 1081386441
> [26ac8df4] rt_sigprocmask(SIG_SETMASK, NULL, [RTMIN], 8) = 0
> [26a357cb] write(6,
> "\240\200\243&\0\0\0\0\300\21\16\10`\313\4\10X\0\24\10\0"..., 148) = 148
> [26ac8df4] rt_sigprocmask(SIG_SETMASK, NULL, [RTMIN], 8) = 0
> [26a32854] rt_sigsuspend([] <unfinished ...>
> [26a32854] --- SIGRTMIN (Unknown signal 32) ---
> [26a321f0] <... rt_sigsuspend resumed> ) = -1 EINTR (Interrupted system
> call)
> [26ac8d70] sigreturn()                  = ? (mask now [RTMIN])
> [26b6b8a1] stat64("/var/cfengine/inputs/cfservd.conf",
> {st_dev=makedev(8, 2), st_ino=1629188, st_mode=S_IFREG|0644, st_nlink=1,
> st_uid=0, st_gid=0, st_blksize=4096, st_blocks=8, st_size=800,
> st_atime=2004/04/08-01:01:40, st_mtime=2004/04/08-01:01:14,
> st_ctime=2004/04/08-01:01:14}) = 0
> [26b73211] select(6, [5], NULL, NULL, NULL) = 1 (in [5])
> [26a35a58] accept(5, {sin_family=AF_INET, sin_port=htons(53690),
> sin_addr=inet_addr("198.63.211.235")}}, [16]) = 7
> [26b344cd] time(NULL)                   = 1081386441
> [26ac8df4] rt_sigprocmask(SIG_SETMASK, NULL, [RTMIN], 8) = 0
> [26a32854] rt_sigsuspend([] <unfinished ...>
> [26a32854] --- SIGRTMIN (Unknown signal 32) ---
> [26a321f0] <... rt_sigsuspend resumed> ) = -1 EINTR (Interrupted system
> call)
> [26ac8d70] sigreturn()                  = ? (mask now [RTMIN])
> [26ac8df4] rt_sigprocmask(SIG_SETMASK, NULL, [RTMIN], 8) = 0
> [26a357cb] write(6,
> "\240\200\243&\0\0\0\0\300\21\16\10`\313\4\10\200\371\25"..., 148) = 148
> [26ac8df4] rt_sigprocmask(SIG_SETMASK, NULL, [RTMIN], 8) = 0
> [26a32854] rt_sigsuspend([] <unfinished ...>
> [26a32854] --- SIGRTMIN (Unknown signal 32) ---
> [26a321f0] <... rt_sigsuspend resumed> ) = -1 EINTR (Interrupted system
> call)
> [26ac8d70] sigreturn()                  = ? (mask now [RTMIN])
> [26b73211] select(6, [5], NULL, NULL, NULL) = 1 (in [5])
> [26a35a58] accept(5, {sin_family=AF_INET, sin_port=htons(48041),
> sin_addr=inet_addr("204.225.92.140")}}, [16]) = 3
> [26b344cd] time(NULL)                   = 1081386442
> [26ac8df4] rt_sigprocmask(SIG_SETMASK, NULL, [RTMIN], 8) = 0
> [26a357cb] write(6,
> "\240\200\243&\0\0\0\0\300\21\16\10`\313\4\10\200\371\25"..., 148) = 148
> [26ac8df4] rt_sigprocmask(SIG_SETMASK, NULL, [RTMIN], 8) = 0
> [26a32854] rt_sigsuspend([] <unfinished ...>
> [26a32854] --- SIGSEGV (Segmentation fault) ---
> 
> ------------------------------------------------------------------------
> gdb debugging info
> ------------------------------------------------------------------------
> 
> (gdb) backtrace main 
> #0  0x08069128 in DeleteItemGeneral (list=0x809cbc8, string=0x2c700cb0
> "134.68.220.74", type=regexComplete) at item-ext.c:709
> #1  0x080693e1 in DeleteItemMatching (list=0x2c702e38, string=0x2c702e38
> "") at item-ext.c:769
> #2  0x08051d9e in DeleteConn (conn=0x2c700490) at cfservd.c:3245
> #3  0x0804cc5c in HandleConnection (conn=0x2c700490) at cfservd.c:1118
> #4  0x2c14b060 in pthread_detach () from /lib/libpthread.so.0
> #5  0x2c294bfa in clone () from /lib/libc.so.6
> 
> 
> 
> 
> (gdb) bt full
> #0  0x08069128 in DeleteItemGeneral (list=0x809cbc8, string=0x2c700cb0
> "134.68.220.74", type=regexComplete) at item-ext.c:709
>       ip = (struct Item *) 0x2c702e98
>       last = (struct Item *) 0x0
>       match = 1
>       matchlen = 0
>       rx = {buffer = 0x8197550 "address@hidden", allocated =
> 96, used = 96, syntax = 242428, fastmap = 0x8197148 "Hu\031\b<ä.,", 
>   translate = 0x0, re_nsub = 0, can_be_null = 0, regs_allocated = 0,
> fastmap_accurate = 1, no_sub = 0, not_bol = 0, not_eol = 0,
> newline_anchor = 0}
>       rxcache = {buffer = 0x8197550 "address@hidden",
> allocated = 96, used = 96, syntax = 242428, fastmap = 0x8197148
> "Hu\031\b<ä.,", 
>   translate = 0x0, re_nsub = 0, can_be_null = 0, regs_allocated = 0,
> fastmap_accurate = 1, no_sub = 0, not_bol = 0, not_eol = 0,
> newline_anchor = 0}
>       pmatch = {rm_so = 0, rm_eo = 13}
> #1  0x080693e1 in DeleteItemMatching (list=0x2c702e38, string=0x2c702e38
> "") at item-ext.c:769
> No locals.
> #2  0x08051d9e in DeleteConn (conn=0x2c700490) at cfservd.c:3245
> No locals.
> #3  0x0804cc5c in HandleConnection (conn=0x2c700490) at cfservd.c:1118
>       sigmask = {__val = {0 <repeats 32 times>}}
> #4  0x2c14b060 in pthread_detach () from /lib/libpthread.so.0
> No symbol table info available.
> #5  0x2c294bfa in clone () from /lib/libc.so.6
> No symbol table info available.
> 
> (gdb) disass $eip-0x20 $eip+0x2
> Dump of assembler code from 0x8069108 to 0x806912a:
> 0x08069108 <DeleteItemGeneral+232>:   add    $0x24,%al
> 0x0806910a <DeleteItemGeneral+234>:   arpl   %sp,(%esi)
> 0x0806910c <DeleteItemGeneral+236>:   or     %ecx,(%eax)
> 0x0806910e <DeleteItemGeneral+238>:   mov    %eax,0x4(%esp,1)
> 0x08069112 <DeleteItemGeneral+242>:   call   0x804aad0
> 0x08069117 <DeleteItemGeneral+247>:   mov    0x8(%ebp),%edx
> 0x0806911a <DeleteItemGeneral+250>:   cmp    (%edx),%esi
> 0x0806911c <DeleteItemGeneral+252>:   je     0x806915f
> <DeleteItemGeneral+319>
> 0x0806911e <DeleteItemGeneral+254>:   test   %esi,%esi
> 0x08069120 <DeleteItemGeneral+256>:   je     0x8069145
> <DeleteItemGeneral+293>
> 0x08069122 <DeleteItemGeneral+258>:   mov    0x18(%esi),%eax
> 0x08069125 <DeleteItemGeneral+261>:   mov    0xffffff9c(%ebp),%edx
> 0x08069128 <DeleteItemGeneral+264>:   mov    %eax,0x18(%edx)
> End of assembler dump.
> 
> 
> eagle src # cat -n item-ext.c | grep -n6 709 | head -10
> 703-   703             return true;
> 704-   704             }
> 705-   705          else
> 706-   706             {
> 707-   707             if (ip != NULL)
> 708-   708                {
> 709:   709                last->next = ip->next; 
> 710-   710                free(ip->name);
> 711-   711                if (ip->classes != NULL) 
> 712-   712                   {
> 



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Work: +47 22453272            Email:  address@hidden
Fax : +47 22453205            WWW  :  http://www.iu.hio.no/~mark
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