Garbage in the initrd memory area may result in the unpack routine
accessing memory outside the buffer. The patch adds a check that the
specified area size is not exceeded.
Signed-off-by: Aaro Koskinen <[email protected]>
Cc: stable <[email protected]>
---
The patch prevents the following kernel panic on Amstrad E3:
Unpacking initramfs...
Unable to handle kernel paging request at virtual address c20121a7
pgd = c0004000
[c20121a7] *pgd=00000000
Internal error: Oops: 75 [#1] PREEMPT
last sysfs file:
Modules linked in:
CPU: 0 Not tainted (2.6.34-rc2-00052-gae6be51 #19)
PC is at unpack_to_rootfs+0xac/0x33c
LR is at decompress_method+0x28/0x64
pc : [<c0009858>] lr : [<c015fcc4>] psr: 20000013
sp : c1819f68 ip : 00000000 fp : c0023b88
r10: c20121a7 r9 : c0023b98 r8 : 00000000
r7 : 00300000 r6 : fffede59 r5 : c0023ad8 r4 : 00000000
r3 : 00000000 r2 : 00000001 r1 : c0303034 r0 : 00000000
Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel
Control: 0000317f Table: 10004000 DAC: 00000017
Process swapper (pid: 1, stack limit = 0xc1818270)
Stack: (0xc1819f68 to 0xc181a000)
9f60: 00000000 c03f77ec c00092f8 c03f68fc 00000000 c03f77e0
9f80: c00228fc 00000000 c000a3c8 00000000 00000000 c03f77e0 c00228fc 00000000
9fa0: c000a3c8 00000001 00000000 00000000 00000000 c000a410 c002263c c00283b0
9fc0: 00000000 00000170 c03da678 00000000 c002263c c00228fc 00000000 00000000
9fe0: 00000000 c0008594 00000000 00000000 00000000 c0029f74 8d7cf20a a7ca85e0
[<c0009858>] (unpack_to_rootfs+0xac/0x33c) from [<c000a410>] (populate_rootfs+0x48/0xb0)
[<c000a410>] (populate_rootfs+0x48/0xb0) from [<c00283b0>] (do_one_initcall+0x60/0x1c0)
[<c00283b0>] (do_one_initcall+0x60/0x1c0) from [<c0008594>] (kernel_init+0xa8/0x15c)
[<c0008594>] (kernel_init+0xa8/0x15c) from [<c0029f74>] (kernel_thread_exit+0x0/0x8)
Code: e1a05001 e1a09000 e1a0b00c ea000059 (e5da3000)
---[ end trace da227214a82491b7 ]---
Kernel panic - not syncing: Attempted to kill init!
[<c002e56c>] (unwind_backtrace+0x0/0xec) from [<c02f1a40>] (panic+0x40/0xcc)
[<c02f1a40>] (panic+0x40/0xcc) from [<c004af64>] (do_exit+0x60/0x608)
[<c004af64>] (do_exit+0x60/0x608) from [<c002c8d4>] (die+0x1b4/0x1e4)
[<c002c8d4>] (die+0x1b4/0x1e4) from [<c002f7d8>] (__do_kernel_fault+0x64/0x84)
[<c002f7d8>] (__do_kernel_fault+0x64/0x84) from [<c002fac8>] (do_translation_fault+0x70/0x80)
[<c002fac8>] (do_translation_fault+0x70/0x80) from [<c00282f0>] (do_DataAbort+0x34/0x94)
[<c00282f0>] (do_DataAbort+0x34/0x94) from [<c0028ac0>] (__dabt_svc+0x40/0x60)
Exception stack(0xc1819f20 to 0xc1819f68)
9f20: 00000000 c0303034 00000001 00000000 00000000 c0023ad8 fffede59 00300000
9f40: 00000000 c0023b98 c20121a7 c0023b88 00000000 c1819f68 c015fcc4 c0009858
9f60: 20000013 ffffffff
[<c0028ac0>] (__dabt_svc+0x40/0x60) from [<c0009858>] (unpack_to_rootfs+0xac/0x33c)
[<c0009858>] (unpack_to_rootfs+0xac/0x33c) from [<c000a410>] (populate_rootfs+0x48/0xb0)
[<c000a410>] (populate_rootfs+0x48/0xb0) from [<c00283b0>] (do_one_initcall+0x60/0x1c0)
[<c00283b0>] (do_one_initcall+0x60/0x1c0) from [<c0008594>] (kernel_init+0xa8/0x15c)
[<c0008594>] (kernel_init+0xa8/0x15c) from [<c0029f74>] (kernel_thread_exit+0x0/0x8)
init/initramfs.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/init/initramfs.c b/init/initramfs.c
index 37d3859..223bdaa 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -460,6 +460,8 @@ static char * __init unpack_to_rootfs(char *buf, unsigned len)
}
if (state != Reset)
error("junk in compressed archive");
+ if (my_inptr >= len)
+ break;
this_header = saved_offset + my_inptr;
buf += my_inptr;
len -= my_inptr;
--
1.5.6.5
On Thu, 1 Apr 2010 12:45:46 +0300
Aaro Koskinen <[email protected]> wrote:
> Garbage in the initrd memory area may result in the unpack routine
> accessing memory outside the buffer. The patch adds a check that the
> specified area size is not exceeded.
>
> Signed-off-by: Aaro Koskinen <[email protected]>
> Cc: stable <[email protected]>
> ---
>
> The patch prevents the following kernel panic on Amstrad E3:
>
> Unpacking initramfs...
> Unable to handle kernel paging request at virtual address c20121a7
>
> ...
>
> --- a/init/initramfs.c
> +++ b/init/initramfs.c
> @@ -460,6 +460,8 @@ static char * __init unpack_to_rootfs(char *buf, unsigned len)
> }
> if (state != Reset)
> error("junk in compressed archive");
> + if (my_inptr >= len)
> + break;
> this_header = saved_offset + my_inptr;
> buf += my_inptr;
> len -= my_inptr;
OK, so if I'm understanding this right, the call to
decompress(buf, len, NULL, flush_buffer, NULL, &my_inptr, error);
has gone and generated more output data than it was asked to generate?
If so, isn't that a bug in the decompressor? Which one is your system using?
[ wonders why my_inptr is static, and why the sixth arg to decompress_fn
takes an int* while callers are passing in an unsigned* ]
On Fri, 2 Apr 2010, Andrew Morton wrote:
> On Thu, 1 Apr 2010 12:45:46 +0300
> Aaro Koskinen <[email protected]> wrote:
>
>> Garbage in the initrd memory area may result in the unpack routine
>> accessing memory outside the buffer. The patch adds a check that the
>> specified area size is not exceeded.
>>
>> Signed-off-by: Aaro Koskinen <[email protected]>
>> Cc: stable <[email protected]>
>> ---
>>
>> The patch prevents the following kernel panic on Amstrad E3:
>>
>> Unpacking initramfs...
>> Unable to handle kernel paging request at virtual address c20121a7
>>
>> ...
>>
>> --- a/init/initramfs.c
>> +++ b/init/initramfs.c
>> @@ -460,6 +460,8 @@ static char * __init unpack_to_rootfs(char *buf, unsigned len)
>> }
>> if (state != Reset)
>> error("junk in compressed archive");
>> + if (my_inptr >= len)
>> + break;
>> this_header = saved_offset + my_inptr;
>> buf += my_inptr;
>> len -= my_inptr;
>
> OK, so if I'm understanding this right, the call to
>
> decompress(buf, len, NULL, flush_buffer, NULL, &my_inptr, error);
>
> has gone and generated more output data than it was asked to generate?
>
> If so, isn't that a bug in the decompressor? Which one is your system using?
The decompressor is gzip, and it returned correct buffer position.
The problem was that the loop in unpack_to_rootfs() continued
to process the remaining buffer. my_inptr was never again updated
(decompress_method() did not recognize the remaining garbage data, so
there was no further calls to decompressor). The loop kept subtracting
my_inptr from len eventually exceeding it. Perhaps there should be some
better logic to give up earlier.
A.