linux-kernel - [PATCH 5.3 034/135] bpf: Change size to u64 for bpf_map_{area_alloc, charge

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Message-Id: <20191203213013.072938572@linuxfoundation.org>
Date:   Tue,  3 Dec 2019 23:34:34 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Björn Töpel <bjorn.topel@...el.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.3 034/135] bpf: Change size to u64 for bpf_map_{area_alloc, charge_init}()

From: Björn Töpel <bjorn.topel@...el.com>

[ Upstream commit ff1c08e1f74b6864854c39be48aa799a6a2e4d2b ]

The functions bpf_map_area_alloc() and bpf_map_charge_init() prior
this commit passed the size parameter as size_t. In this commit this
is changed to u64.

All users of these functions avoid size_t overflows on 32-bit systems,
by explicitly using u64 when calculating the allocation size and
memory charge cost. However, since the result was narrowed by the
size_t when passing size and cost to the functions, the overflow
handling was in vain.

Instead of changing all call sites to size_t and handle overflow at
the call site, the parameter is changed to u64 and checked in the
functions above.

Fixes: d407bd25a204 ("bpf: don't trigger OOM killer under pressure with map alloc")
Fixes: c85d69135a91 ("bpf: move memory size checks to bpf_map_charge_init()")
Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
Link: https://lore.kernel.org/bpf/20191029154307.23053-1-bjorn.topel@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/linux/bpf.h  | 4 ++--
 kernel/bpf/syscall.c | 7 +++++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 18f4cc2c6acd4..5d177c0c7fe37 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -651,11 +651,11 @@ void bpf_map_put_with_uref(struct bpf_map *map);
 void bpf_map_put(struct bpf_map *map);
 int bpf_map_charge_memlock(struct bpf_map *map, u32 pages);
 void bpf_map_uncharge_memlock(struct bpf_map *map, u32 pages);
-int bpf_map_charge_init(struct bpf_map_memory *mem, size_t size);
+int bpf_map_charge_init(struct bpf_map_memory *mem, u64 size);
 void bpf_map_charge_finish(struct bpf_map_memory *mem);
 void bpf_map_charge_move(struct bpf_map_memory *dst,
 			 struct bpf_map_memory *src);
-void *bpf_map_area_alloc(size_t size, int numa_node);
+void *bpf_map_area_alloc(u64 size, int numa_node);
 void bpf_map_area_free(void *base);
 void bpf_map_init_from_attr(struct bpf_map *map, union bpf_attr *attr);
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index aac966b32c42e..ee3087462bc97 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -126,7 +126,7 @@ static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
 	return map;
 }
 
-void *bpf_map_area_alloc(size_t size, int numa_node)
+void *bpf_map_area_alloc(u64 size, int numa_node)
 {
 	/* We really just want to fail instead of triggering OOM killer
 	 * under memory pressure, therefore we set __GFP_NORETRY to kmalloc,
@@ -141,6 +141,9 @@ void *bpf_map_area_alloc(size_t size, int numa_node)
 	const gfp_t flags = __GFP_NOWARN | __GFP_ZERO;
 	void *area;
 
+	if (size >= SIZE_MAX)
+		return NULL;
+
 	if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) {
 		area = kmalloc_node(size, GFP_USER | __GFP_NORETRY | flags,
 				    numa_node);
@@ -197,7 +200,7 @@ static void bpf_uncharge_memlock(struct user_struct *user, u32 pages)
 		atomic_long_sub(pages, &user->locked_vm);
 }
 
-int bpf_map_charge_init(struct bpf_map_memory *mem, size_t size)
+int bpf_map_charge_init(struct bpf_map_memory *mem, u64 size)
 {
 	u32 pages = round_up(size, PAGE_SIZE) >> PAGE_SHIFT;
 	struct user_struct *user;
-- 
2.20.1