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Date: Thu, 04 Nov 2010 15:27:59 +0800
From: Eugene Teo <>
CC: "Steven M. Christey" <>
Subject: Re: CVE request: kernel: sys_semctl: fix kernel stack

On 11/04/2010 02:40 PM, Eugene Teo wrote:
> "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:
> Credit: Dan Rosenberg
> Reference:

Whoops, this has been assigned CVE-2010-4083.

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

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