objpool intends to use vmalloc for default (non-atomic) allocations of percpu slots and objects. However, the condition checking if GFP flags set any bit of GFP_ATOMIC is wrong b/c GFP_ATOMIC is a combination of bits (__GFP_HIGH|__GFP_KSWAPD_RECLAIM) and so `pool->gfp & GFP_ATOMIC` will be true if either bit is set. Since GFP_ATOMIC and GFP_KERNEL share the ___GFP_KSWAPD_RECLAIM bit, kmalloc will be used in cases when GFP_KERNEL is specified, i.e. in all current usages of objpool. This may lead to unexpected OOM errors since kmalloc cannot allocate large amounts of memory. For instance, objpool is used by fprobe rethook which in turn is used by BPF kretprobe.multi and kprobe.session probe types. Trying to attach these to all kernel functions with libbpf using SEC("kprobe.session/*") int kprobe(struct pt_regs *ctx) { [...] } fails on objpool slot allocation with ENOMEM. Fix the condition to truly use vmalloc by default. Link: https://lore.kernel.org/all/20240826060718.267261-1-vmalik@redhat.com/
Unified · Split
| @@ -76,7 +76,7 @@ objpool_init_percpu_slots(struct objpool_head *pool, int nr_objs, · 75 unmodified lines | ||
| 76 | 76 | * mimimal size of vmalloc is one page since vmalloc would |
| 77 | 77 | * always align the requested size to page size |
| 78 | 78 | */ |
| 79 | − if (pool->gfp & GFP_ATOMIC) | |
| 79 | + if ((pool->gfp & GFP_ATOMIC) == GFP_ATOMIC) | |
| 80 | 80 | slot = kmalloc_node(size, pool->gfp, cpu_to_node(i)); |
| 81 | 81 | else |
| 82 | 82 | slot = __vmalloc_node(size, sizeof(void *), pool->gfp, |