148 lines
4.2 KiB
Diff
148 lines
4.2 KiB
Diff
From: Alexei Starovoitov <ast@fb.com>
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Date: Wed, 27 Apr 2016 18:56:20 -0700
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Subject: [2/3] bpf: fix refcnt overflow
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Origin: https://git.kernel.org/linus/92117d8443bc5afacc8d5ba82e541946310f106e
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On a system with >32Gbyte of phyiscal memory and infinite RLIMIT_MEMLOCK,
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the malicious application may overflow 32-bit bpf program refcnt.
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It's also possible to overflow map refcnt on 1Tb system.
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Impose 32k hard limit which means that the same bpf program or
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map cannot be shared by more than 32k processes.
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Fixes: 1be7f75d1668 ("bpf: enable non-root eBPF programs")
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Reported-by: Jann Horn <jannh@google.com>
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Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Acked-by: Daniel Borkmann <daniel@iogearbox.net>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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include/linux/bpf.h | 3 ++-
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kernel/bpf/inode.c | 7 ++++---
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kernel/bpf/syscall.c | 24 ++++++++++++++++++++----
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kernel/bpf/verifier.c | 11 +++++++----
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4 files changed, 33 insertions(+), 12 deletions(-)
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--- a/include/linux/bpf.h
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+++ b/include/linux/bpf.h
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@@ -165,12 +165,13 @@ void bpf_register_prog_type(struct bpf_p
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void bpf_register_map_type(struct bpf_map_type_list *tl);
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struct bpf_prog *bpf_prog_get(u32 ufd);
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+struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog);
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void bpf_prog_put(struct bpf_prog *prog);
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void bpf_prog_put_rcu(struct bpf_prog *prog);
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struct bpf_map *bpf_map_get_with_uref(u32 ufd);
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struct bpf_map *__bpf_map_get(struct fd f);
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-void bpf_map_inc(struct bpf_map *map, bool uref);
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+struct bpf_map *bpf_map_inc(struct bpf_map *map, bool uref);
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void bpf_map_put_with_uref(struct bpf_map *map);
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void bpf_map_put(struct bpf_map *map);
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--- a/kernel/bpf/inode.c
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+++ b/kernel/bpf/inode.c
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@@ -31,10 +31,10 @@ static void *bpf_any_get(void *raw, enum
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{
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switch (type) {
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case BPF_TYPE_PROG:
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- atomic_inc(&((struct bpf_prog *)raw)->aux->refcnt);
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+ raw = bpf_prog_inc(raw);
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break;
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case BPF_TYPE_MAP:
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- bpf_map_inc(raw, true);
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+ raw = bpf_map_inc(raw, true);
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break;
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default:
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WARN_ON_ONCE(1);
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@@ -297,7 +297,8 @@ static void *bpf_obj_do_get(const struct
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goto out;
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raw = bpf_any_get(inode->i_private, *type);
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- touch_atime(&path);
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+ if (!IS_ERR(raw))
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+ touch_atime(&path);
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path_put(&path);
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return raw;
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--- a/kernel/bpf/syscall.c
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+++ b/kernel/bpf/syscall.c
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@@ -201,11 +201,18 @@ struct bpf_map *__bpf_map_get(struct fd
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return f.file->private_data;
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}
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-void bpf_map_inc(struct bpf_map *map, bool uref)
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+/* prog's and map's refcnt limit */
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+#define BPF_MAX_REFCNT 32768
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+
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+struct bpf_map *bpf_map_inc(struct bpf_map *map, bool uref)
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{
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- atomic_inc(&map->refcnt);
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+ if (atomic_inc_return(&map->refcnt) > BPF_MAX_REFCNT) {
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+ atomic_dec(&map->refcnt);
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+ return ERR_PTR(-EBUSY);
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+ }
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if (uref)
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atomic_inc(&map->usercnt);
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+ return map;
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}
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struct bpf_map *bpf_map_get_with_uref(u32 ufd)
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@@ -217,7 +224,7 @@ struct bpf_map *bpf_map_get_with_uref(u3
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if (IS_ERR(map))
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return map;
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- bpf_map_inc(map, true);
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+ map = bpf_map_inc(map, true);
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fdput(f);
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return map;
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@@ -600,6 +607,15 @@ static struct bpf_prog *__bpf_prog_get(s
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return f.file->private_data;
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}
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+struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog)
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+{
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+ if (atomic_inc_return(&prog->aux->refcnt) > BPF_MAX_REFCNT) {
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+ atomic_dec(&prog->aux->refcnt);
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+ return ERR_PTR(-EBUSY);
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+ }
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+ return prog;
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+}
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+
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/* called by sockets/tracing/seccomp before attaching program to an event
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* pairs with bpf_prog_put()
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*/
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@@ -612,7 +628,7 @@ struct bpf_prog *bpf_prog_get(u32 ufd)
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if (IS_ERR(prog))
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return prog;
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- atomic_inc(&prog->aux->refcnt);
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+ prog = bpf_prog_inc(prog);
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fdput(f);
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return prog;
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--- a/kernel/bpf/verifier.c
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+++ b/kernel/bpf/verifier.c
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@@ -2022,15 +2022,18 @@ static int replace_map_fd_with_map_ptr(s
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return -E2BIG;
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}
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- /* remember this map */
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- env->used_maps[env->used_map_cnt++] = map;
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-
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/* hold the map. If the program is rejected by verifier,
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* the map will be released by release_maps() or it
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* will be used by the valid program until it's unloaded
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* and all maps are released in free_bpf_prog_info()
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*/
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- bpf_map_inc(map, false);
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+ map = bpf_map_inc(map, false);
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+ if (IS_ERR(map)) {
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+ fdput(f);
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+ return PTR_ERR(map);
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+ }
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+ env->used_maps[env->used_map_cnt++] = map;
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+
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fdput(f);
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next_insn:
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insn++;
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