Re: [PATCH] powerpc/mm: Don't see NULL pointer dereference as a KUAP fault

2020-12-03 Thread Christophe Leroy
Le 03/12/2020 à 12:55, Michael Ellerman a écrit : Christophe Leroy writes: Sometimes, NULL pointer dereferences are expected. Even when they are accidental they are unlikely an exploit attempt because the first page is never mapped. The first page can be mapped if mmap_min_addr is 0. Bloc

Re: [PATCH] powerpc/mm: Don't see NULL pointer dereference as a KUAP fault

2020-12-03 Thread Michael Ellerman
Christophe Leroy writes: > Sometimes, NULL pointer dereferences are expected. Even when they > are accidental they are unlikely an exploit attempt because the > first page is never mapped. The first page can be mapped if mmap_min_addr is 0. Blocking all faults to the first page would potentially

[PATCH] powerpc/mm: Don't see NULL pointer dereference as a KUAP fault

2020-12-01 Thread Christophe Leroy
Sometimes, NULL pointer dereferences are expected. Even when they are accidental they are unlikely an exploit attempt because the first page is never mapped. The exemple below shows what we get when invoking the "show task" sysrq handler, by writing 't' in /proc/sysrq-trigger [ 1117.202054] -