OpenBSD procfs

["Deprotect Advisories" <advisories () deprotect com>]

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Deprotect Security Advisory 20041405
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Advisory ID  : DEPROTECT-20041405
Authors      : Christer Oberg, Joel Soderberg
Publish date : 17/05/2004
Application  : Procfs
Version(s)   : 3.5 (and earlier versions)
Platforms    : OpenBSD
CVE#         :
Availability : http://www.deprotect.com/advisories/DEPROTECT-20041305.txt
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Problem:
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Kernel memory disclosure via procfs. 


Description:
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Several integer related bugs in the procfs code can lead to kernel
memory disclosure. For example it is possible to trick procfs to return
large chunks of kernel memory when reading the cmdline file of system
processes. 

This code is found in procfs_cmdline.c: 

        if (P_ZOMBIE(p) || (p->p_flag & P_SYSTEM) != 0) {
              len = snprintf(arg, PAGE_SIZE, "(%s)", p->p_comm);
              xlen = len - uio->uio_offset;
              if (xlen <= 0)
                      error = 0;
              else
                      error = uiomove(arg, xlen, uio);
                free(arg, M_TEMP);
              return (error);   
	} 


It is trivial to for example pread() the descriptor with an offset and
have it return more data than it should. There are other examples of
similar bugs in the procfs code. 



Workaround:
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Unmount procfs. 


Fix:
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Patch available at http://www.openbsd.org/errata.html 


Disclosure Timeline:
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03/05/2004: Initial email to vendor.
13/05/2004: Patch made available (without telling us)



About Deprotect:
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Contacting Deprotect:
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Homepage:  http://www.deprotect.com/
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