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authorDaniel Borkmann <daniel@iogearbox.net>2017-04-17 03:12:07 +0200
committerDavid S. Miller <davem@davemloft.net>2017-04-17 15:51:57 -0400
commitc2002f983767ea0a53acbb3e21f771e7a7e2ed28 (patch)
parent6b1bb01bcc5be91452bd3b5bda4300f179fd4053 (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>
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