oss-security - CVE request: kernel: sys_semctl: fix kernel stack leakage

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Date: Thu, 04 Nov 2010 14:40:38 +0800
From: Eugene Teo <eugene@...hat.com>
To: oss-security@...ts.openwall.com
CC: "Steven M. Christey" <coley@...us.mitre.org>
Subject: CVE request: kernel: sys_semctl: fix kernel stack leakage

"The semctl syscall has several code paths that lead to the leakage of
uninitialized kernel stack memory (namely the IPC_INFO, SEM_INFO,
IPC_STAT, and SEM_STAT commands) during the use of the older, obsolete
version of the semid_ds struct.

The copy_semid_to_user() function declares a semid_ds struct on the 
stack and copies it back to the user without initializing or zeroing the
"sem_base", "sem_pending", "sem_pending_last", and "undo" pointers,
allowing the leakage of 16 bytes of kernel stack memory.

The code is still reachable on 32-bit systems - when calling semctl()
newer glibc's automatically OR the IPC command with the IPC_64 flag, but
invoking the syscall directly allows users to use the older versions of
the struct."

Upstream commit:
http://git.kernel.org/linus/982f7c2b2e6a28f8f266e075d92e19c0dd4c6e56

Credit: Dan Rosenberg

Reference:
https://bugzilla.redhat.com/show_bug.cgi?id=649614

Thanks, Eugene
-- 
main(i) { putchar(182623909 >> (i-1) * 5&31|!!(i<7)<<6) && main(++i); }

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