Re: 2.6.37-rc7: Regression: b43: crashes in hwrng_register()

Larry Finger
2010-12-30T18:37:27Z

[-- Attachment #1: Type: text/plain, Size: 3281 bytes --]

On 12/30/2010 08:34 AM, Mario 'BitKoenig' Holbe wrote:
> On Wed, Dec 29, 2010 at 08:37:10PM -0600, Larry Finger wrote:
>> No, don't bother. I do have a different request. The byte counts for my 32-bit
>> system do not match yours. Could you please use the following command to find
>> the instructions that are failing?
>>
>> objdump -l -d drivers/char/hw_random/core.o | less
>>
>> Use the search to find the start of hwrng_register, then add 0x4c to the
>> starting address. Once I see hte instruction that is failing, I should be able
>> to find where the failure occurs.
>
> Alright, here we go...
>
> [ 30.012695] BUG: unable to handle kernel paging request at 4b28f458
> [ 30.012708] IP: [<f90703cc>] hwrng_register+0x4c/0x139 [rng_core]
>
> 00000380 <hwrng_register>:
> hwrng_register():
> /tmp/1/linux-source-2.6.37-rc7/drivers/char/hw_random/core.c:299
> 380: 56 push %esi
> 381: 53 push %ebx
> ...
> /tmp/1/linux-source-2.6.37-rc7/drivers/char/hw_random/core.c:312
> 3c6: 8b 76 1c mov 0x1c(%esi),%esi
> 3c9: 83 ee 1c sub $0x1c,%esi
> prefetch():
> /tmp/1/linux-source-2.6.37-rc7/arch/x86/include/asm/processor.h:837
> 3cc: 8b 46 1c mov 0x1c(%esi),%eax
> 3cf: 8d 74 26 00 lea 0x0(%esi,%eiz,1),%esi
> hwrng_register():
> /tmp/1/linux-source-2.6.37-rc7/drivers/char/hw_random/core.c:312
> 3d3: 81 fe f8 ff ff ff cmp $0xfffffff8,%esi
> 3d9: 75 d4 jne 3af <hwrng_register+0x2f>
> /tmp/1/linux-source-2.6.37-rc7/drivers/char/hw_random/core.c:319
>
> 312 list_for_each_entry(tmp, &rng_list, list) {
> 313 if (strcmp(tmp->name, rng->name) == 0)
> 314 goto out_unlock;
> 315 }
>
> This is btw. the same data that is accessed in the cat rng_available
> crash via hwrng_attr_available_show():
>
> [ 389.303538] BUG: unable to handle kernel paging request at 288dcb5b
> [ 389.303553] IP: [<f8dda34c>] hwrng_attr_available_show+0x5c/0x90 [rng_core]
>
> 000002f0 <hwrng_attr_available_show>:
> hwrng_attr_available_show():
> /tmp/1/linux-source-2.6.37-rc7/drivers/char/hw_random/core.c:236
> 2f0: 55 push %ebp
> ...
> /tmp/1/linux-source-2.6.37-rc7/drivers/char/hw_random/core.c:245
> 346: 8b 5b 1c mov 0x1c(%ebx),%ebx
> 349: 83 eb 1c sub $0x1c,%ebx
> prefetch():
> /tmp/1/linux-source-2.6.37-rc7/arch/x86/include/asm/processor.h:837
> 34c: 8b 43 1c mov 0x1c(%ebx),%eax
> 34f: 8d 74 26 00 lea 0x0(%esi,%eiz,1),%esi
> hwrng_attr_available_show():
> /tmp/1/linux-source-2.6.37-rc7/drivers/char/hw_random/core.c:245
>
> 245 list_for_each_entry(rng, &rng_list, list) {
> 246 strncat(buf, rng->name, PAGE_SIZE - ret - 1);
> 247 ret += strlen(rng->name);
> 248 strncat(buf, " ", PAGE_SIZE - ret - 1);
> 249 ret++;
> 250 }

The head of the rng_list is damaged. It is initialized at compile time and
should be OK. To help discover the order in which hwrng_register() is called,
apply the attached patch. Run it once with commit 84c164a34ffe67908a installed,
and once with it reverted.

Thanks,

Larry

[-- Attachment #2: hwrng_debug --]
[-- Type: text/plain, Size: 822 bytes --]

Index: wireless-testing/drivers/char/hw_random/core.c
===================================================================
--- wireless-testing.orig/drivers/char/hw_random/core.c
+++ wireless-testing/drivers/char/hw_random/core.c
@@ -49,11 +49,11 @@

static struct hwrng *current_rng;
-static LIST_HEAD(rng_list);
static DEFINE_MUTEX(rng_mutex);
static int data_avail;
static u8 rng_buffer[SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES]
__cacheline_aligned;
+static LIST_HEAD(rng_list);

static inline int hwrng_init(struct hwrng *rng)
{
@@ -305,6 +305,9 @@ int hwrng_register(struct hwrng *rng)
(rng->data_read == NULL && rng->read == NULL))
goto out;

+ printk(KERN_INFO "Calling hwrng_register\n");
+ dump_stack();
+
mutex_lock(&rng_mutex);

/* Must not register two RNGs with the same name. */