[PATCH] Fix __minimal_malloc segfaults in __mmap due to stack-protector

[Stefan Liebler]

On 16/12/2021 12:54, Siddhesh Poyarekar wrote:
> On 12/16/21 17:17, Stefan Liebler via Libc-alpha wrote:
>> Starting with commit b05fae4d8e34604a72ee36d2d3164391b76fcf0b
>> "elf: Use the minimal malloc on tunables_strdup",
>> I get lots of segfaults in static tests on s390x when also using, e.g.:
>> export GLIBC_TUNABLES="glibc.elision.enable=1"
>>
>> tunables_strdup callls __minimal_malloc which tries to call __mmap
>> due to insufficient space left. __mmap itself first setups a new
>> stack frame and segfaults when copying the stack-protector canary
>> from thread-pointer. The latter one is not yet setup.
>>
>> Thus this patch also turns off stack-protection for mmap.
> 
> LGTM.
> 
> Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> 
>> ---
>>   misc/Makefile | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/misc/Makefile b/misc/Makefile
>> index 3b66cb9f6a..db40312ba9 100644
>> --- a/misc/Makefile
>> +++ b/misc/Makefile
>> @@ -149,6 +149,10 @@ CFLAGS-sbrk.o = $(no-stack-protector)
>>   CFLAGS-sbrk.op = $(no-stack-protector)
>>   CFLAGS-brk.o = $(no-stack-protector)
>>   CFLAGS-brk.op = $(no-stack-protector)
>> +CFLAGS-mmap.o = $(no-stack-protector)
>> +CFLAGS-mmap.op = $(no-stack-protector)
>> +CFLAGS-mmap64.o = $(no-stack-protector)
>> +CFLAGS-mmap64.op = $(no-stack-protector)
>>     include ../Rules
>>  
> 
Committed.
Thanks