Commit 7984c27c authored Jan 10, 2017 by Michal Hocko Committed by Linus Torvalds Jan 10, 2017

bpf: do not use KMALLOC_SHIFT_MAX

Commit 01b3f521 ("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.

The original motivation for using KMALLOC_SHIFT_MAX was to work around
an incorrect KMALLOC_MAX_SIZE which could lead to allocation warnings
but it is no longer needed since "slab: make sure that KMALLOC_MAX_SIZE
will fit into MAX_ORDER".

Link: http://lkml.kernel.org/r/20161220130659.16461-3-mhocko@kernel.org


Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent bb1107f7

kernel/bpf/arraymap.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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.
		*/

kernel/bpf/hashtab.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -274,7 +274,7 @@ 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

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