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Vulnerability of Linux kernel: incorrect reseed of xfer_secondary_pool

Synthesis of the vulnerability 

The xfer_secondary_pool() function does not correctly reseed a buffer containing random data.
Vulnerable systems: Debian, Linux.
Severity of this threat: 2/4.
Creation date: 23/07/2007.
Références of this weakness: BID-25029, CVE-2007-4311, DSA-1503-1, VIGILANCE-VUL-7028.

Description of the vulnerability 

The xfer_secondary_pool() function of drivers/char/random.c transfers entropy between two pools. In order to do so, a temporary buffer named tmp of TMP_BUF_SIZE(340) bytes is used.

The size to reseed is computed from sizeof(tmp). However, as the buffer is located outside the xfer_secondary_pool() function, a pointer is given, so sizeof(tmp) is 4 instead of 340.

Some random data used by application may thus be predictable.
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This computer threat impacts software or systems such as Debian, Linux.

Our Vigil@nce team determined that the severity of this computer vulnerability alert is medium.

The trust level is of type confirmed by the editor, with an origin of document.

An attacker with a expert ability can exploit this cybersecurity weakness.

Solutions for this threat 

Linux kernel: version 2.4.35.
Version 2.4.35 is corrected:
  http://www.kernel.org/

Linux kernel: version 2.4.34.6.
Version 2.4.34.6 is corrected:
  http://www.kernel.org/

Debian 3.1: new kernel-2.4.27 packages.
New packages are available:
  http://security.debian.org/pool/updates/main/k/kernel-*_2.4.27-10sarge7
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