From: Barry Song <v-songbaohua@xxxxxxxx> -v2: * adjust vpda fix according to Jason and Michal's feedback, I would expect Jason to test it, thanks! * split BUG_ON of unavoidable failure and the case GFP_ATOMIC | __GFP_NOFAIL into two patches according to Vlastimil and Michal. * collect Michal's acked-by for patch 2 - the doc; * remove the new GFP_NOFAIL from this series, that one would be a separate enhancement patchset later on. -v1: https://lore.kernel.org/linux-mm/20240724085544.299090-1-21cnbao@xxxxxxxxx/ __GFP_NOFAIL carries the semantics of never failing, so its callers do not check the return value: %__GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller cannot handle allocation failures. The allocation could block indefinitely but will never return with failure. Testing for failure is pointless. However, __GFP_NOFAIL can sometimes fail if it exceeds size limits or is used with GFP_ATOMIC/GFP_NOWAIT in a non-sleepable context. This can expose security vulnerabilities due to potential NULL dereferences. Since __GFP_NOFAIL does not support non-blocking allocation, we introduce GFP_NOFAIL with inclusive blocking semantics and encourage using GFP_NOFAIL as a replacement for __GFP_NOFAIL in non-mm. If we must still fail a nofail allocation, we should trigger a BUG rather than exposing NULL dereferences to callers who do not check the return value. * The discussion started from this topic: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL https://lore.kernel.org/linux-mm/20240717230025.77361-1-21cnbao@xxxxxxxxx/ Thank you to Michal, Christoph, Vlastimil, and Hailong for all the comments. Barry Song (4): vpda: try to fix the potential crash due to misusing __GFP_NOFAIL mm: Document __GFP_NOFAIL must be blockable mm: BUG_ON to avoid NULL deference while __GFP_NOFAIL fails mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL drivers/vdpa/vdpa_user/iova_domain.c | 31 +++++++++++++++++++++++----- drivers/vdpa/vdpa_user/iova_domain.h | 5 ++++- drivers/vdpa/vdpa_user/vduse_dev.c | 4 +++- include/linux/gfp_types.h | 5 ++++- include/linux/slab.h | 4 +++- mm/page_alloc.c | 14 +++++++------ mm/util.c | 1 + 7 files changed, 49 insertions(+), 15 deletions(-) -- 2.34.1
