diff options
author | Daniel Borkmann | 2017-04-17 03:12:07 +0200 |
---|---|---|
committer | David S. Miller | 2017-04-17 15:51:57 -0400 |
commit | c2002f983767ea0a53acbb3e21f771e7a7e2ed28 (patch) | |
tree | 82226511f5f60faf8c8bf820051da232e104c026 | |
parent | 6b1bb01bcc5be91452bd3b5bda4300f179fd4053 (diff) |
bpf: fix checking xdp_adjust_head on tail calls
Commit 17bedab27231 ("bpf: xdp: Allow head adjustment in XDP prog")
added the xdp_adjust_head bit to the BPF prog in order to tell drivers
that the program that is to be attached requires support for the XDP
bpf_xdp_adjust_head() helper such that drivers not supporting this
helper can reject the program. There are also drivers that do support
the helper, but need to check for xdp_adjust_head bit in order to move
packet metadata prepended by the firmware away for making headroom.
For these cases, the current check for xdp_adjust_head bit is insufficient
since there can be cases where the program itself does not use the
bpf_xdp_adjust_head() helper, but tail calls into another program that
uses bpf_xdp_adjust_head(). As such, the xdp_adjust_head bit is still
set to 0. Since the first program has no control over which program it
calls into, we need to assume that bpf_xdp_adjust_head() helper is used
upon tail calls. Thus, for the very same reasons in cb_access, set the
xdp_adjust_head bit to 1 when the main program uses tail calls.
Fixes: 17bedab27231 ("bpf: xdp: Allow head adjustment in XDP prog")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r-- | kernel/bpf/syscall.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index ee5c969d5963..821f9e807de5 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -623,6 +623,7 @@ static void fixup_bpf_calls(struct bpf_prog *prog) * in the program array. */ prog->cb_access = 1; + prog->xdp_adjust_head = 1; /* mark bpf_tail_call as different opcode * to avoid conditional branch in |