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bpf: add missing rcu protection when releasing programs from prog_array

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Normally the program attachment place (like sockets, qdiscs) takes
care of rcu protection and calls bpf_prog_put() after a grace period.
The programs stored inside prog_array may not be attached anywhere,
so prog_array needs to take care of preserving rcu protection.
Otherwise bpf_tail_call() will race with bpf_prog_put().
To solve that introduce bpf_prog_put_rcu() helper function and use
it in 3 places where unattached program can decrement refcnt:
closing program fd, deleting/replacing program in prog_array.

Fixes: 04fd61ab36 ("bpf: allow bpf programs to tail-call other bpf programs")
Reported-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov 2015-05-28 19:26:02 -07:00 • committed by David S. Miller
parent d1f5f2bb91
commit abf2e7d6e2
3 changed files with 25 additions and 4 deletions
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6
include/linux/bpf.h
View file

@ -123,7 +123,10 @@ struct bpf_prog_aux {
const struct bpf_verifier_ops *ops;
struct bpf_map **used_maps;
struct bpf_prog *prog;
struct work_struct work;
union {
struct work_struct work;
struct rcu_head rcu;
};
};
struct bpf_array {
@ -153,6 +156,7 @@ void bpf_register_map_type(struct bpf_map_type_list *tl);
struct bpf_prog *bpf_prog_get(u32 ufd);
void bpf_prog_put(struct bpf_prog *prog);
void bpf_prog_put_rcu(struct bpf_prog *prog);
struct bpf_map *bpf_map_get(struct fd f);
void bpf_map_put(struct bpf_map *map);