Re: [PATCH 1/2] bpf: do not use KMALLOC_SHIFT_MAX
From: Alexei Starovoitov <hidden>
Date: 2016-12-16 18:02:17
Also in:
linux-mm
On Thu, Dec 15, 2016 at 05:47:21PM +0100, Michal Hocko wrote:
From: Michal Hocko <mhocko@suse.com>
01b3f52157ff ("bpf: fix allocation warnings in bpf maps and integer
overflow") has added checks for the maximum allocateable size. It
(ab)used KMALLOC_SHIFT_MAX for that purpose. While this is not incorrect
it is not very clean because we already have KMALLOC_MAX_SIZE for this
very reason so let's change both checks to use KMALLOC_MAX_SIZE instead.
Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Michal Hocko <mhocko@suse.com>Nack until the patches 1 and 2 are reversed. The bug that patch 2 fixes was the reason we used KMALLOC_SHIFT_MAX - 1 here instead of KMALLOC_MAX_SIZE, so you have to fix the kmalloc vs __alloc_pages_slowpath discrepancy first.
quoted hunk
--- kernel/bpf/arraymap.c | 2 +- kernel/bpf/hashtab.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index a2ac051c342f..229a5d5df977 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c@@ -56,7 +56,7 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr) attr->value_size == 0 || attr->map_flags) return ERR_PTR(-EINVAL); - if (attr->value_size >= 1 << (KMALLOC_SHIFT_MAX - 1)) + if (attr->value_size > KMALLOC_MAX_SIZE) /* if value_size is bigger, the user space won't be able to * access the elements. */diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index ad1bc67aff1b..c5ec7dc71c84 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c@@ -181,7 +181,7 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) */ goto free_htab; - if (htab->map.value_size >= (1 << (KMALLOC_SHIFT_MAX - 1)) - + if (htab->map.value_size >= KMALLOC_MAX_SIZE - MAX_BPF_STACK - sizeof(struct htab_elem)) /* if value_size is bigger, the user space won't be able to * access the elements via bpf syscall. This check also makes-- 2.10.2
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