> Fixes: 14cf11af6cf6 ("powerpc: Merge enough to start building in
> arch/powerpc.")
Wow, that's pretty ancient! I'm also not sure it's right - in that same
patch, arch/ppc64/mm/fault.c contains:
^1da177e4c3f4 (Linus Torvalds 2005-04-16 15:20:36 -0700 213)
if (address + 2048 < uregs->gpr[1]
^1da177e4c3f4 (Linus Torvalds 2005-04-16 15:20:36 -0700 214)
&& (!user_mode(regs) || !store_updates_sp(regs)))
^1da177e4c3f4 (Linus Torvalds 2005-04-16 15:20:36 -0700 215)
goto bad_area;
Which is the same as the new arch/powerpc/mm/fault.c code:
14cf11af6cf60 (Paul Mackerras 2005-09-26 16:04:21 +1000 234) if
(address + 2048 < uregs->gpr[1]
14cf11af6cf60 (Paul Mackerras 2005-09-26 16:04:21 +1000 235) &&
(!user_mode(regs) || !store_updates_sp(regs)))
14cf11af6cf60 (Paul Mackerras 2005-09-26 16:04:21 +1000 236)
goto bad_area;
So either they're both right or they're both wrong, either way I'm not
sure how this patch is to blame.
I guess we should also cc stable@...
Regards,
Daniel
>> Reported-by: Tom Lane <t...@sss.pgh.pa.us>
>> Cc: Daniel Black <dan...@linux.ibm.com>
>> Signed-off-by: Daniel Axtens <d...@axtens.net>
>> ---
>> arch/powerpc/mm/fault.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
>> index b5047f9b5dec..00183731ea22 100644
>> --- a/arch/powerpc/mm/fault.c
>> +++ b/arch/powerpc/mm/fault.c
>> @@ -287,7 +287,17 @@ static bool bad_stack_expansion(struct pt_regs *regs,
>> unsigned long address,
>> if (!res)
>> return !store_updates_sp(inst);
>> *must_retry = true;
>> + } else if ((flags & FAULT_FLAG_WRITE) &&
>> + !(flags & FAULT_FLAG_USER)) {
>> + /*
>> + * the kernel can also attempt to write beyond the end
>> + * of a process's stack - for example setting up a
>> + * signal frame. We assume this is valid, subject to
>> + * the checks in expand_stack() later.
>> + */
>> + return false;
>> }
>> +
>> return true;
>> }
>> return false;
>> --
>> 2.20.1
>>
