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| author | Kris Van Hees <kris.van.hees@oracle.com> | 2022-01-06 00:01:50 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-01-27 13:03:51 +0300 |
| commit | 2fbd466952728c088cb1b430256afa8d5c58615b (patch) | |
| tree | e9cf9b21a71ab93f1355623cf6e7ab65183abad5 /kernel/bpf | |
| parent | a65df848dbe083bfe1c01200b6b5038083824872 (diff) | |
| download | linux-2fbd466952728c088cb1b430256afa8d5c58615b.tar.xz | |
bpf: Fix verifier support for validation of async callbacks
[ Upstream commit a5bebc4f00dee47113eed48098c68e88b5ba70e8 ]
Commit bfc6bb74e4f1 ("bpf: Implement verifier support for validation of async callbacks.")
added support for BPF_FUNC_timer_set_callback to
the __check_func_call() function. The test in __check_func_call() is
flaweed because it can mis-interpret a regular BPF-to-BPF pseudo-call
as a BPF_FUNC_timer_set_callback callback call.
Consider the conditional in the code:
if (insn->code == (BPF_JMP | BPF_CALL) &&
insn->imm == BPF_FUNC_timer_set_callback) {
The BPF_FUNC_timer_set_callback has value 170. This means that if you
have a BPF program that contains a pseudo-call with an instruction delta
of 170, this conditional will be found to be true by the verifier, and
it will interpret the pseudo-call as a callback. This leads to a mess
with the verification of the program because it makes the wrong
assumptions about the nature of this call.
Solution: include an explicit check to ensure that insn->src_reg == 0.
This ensures that calls cannot be mis-interpreted as an async callback
call.
Fixes: bfc6bb74e4f1 ("bpf: Implement verifier support for validation of async callbacks.")
Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220105210150.GH1559@oracle.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7be72682dfda..94f7f6ac136f 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5785,6 +5785,7 @@ static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn } if (insn->code == (BPF_JMP | BPF_CALL) && + insn->src_reg == 0 && insn->imm == BPF_FUNC_timer_set_callback) { struct bpf_verifier_state *async_cb; |