xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

bpf, xdp: drop rcu_read_lock from bpf_prog_run_xdp and move to caller

Browse Source 
After 326fe02d1e ("net/mlx4_en: protect ring->xdp_prog with rcu_read_lock"),
the rcu_read_lock() in bpf_prog_run_xdp() is superfluous, since callers
need to hold rcu_read_lock() already to make sure BPF program doesn't
get released in the background.

Thus, drop it from bpf_prog_run_xdp(), as it can otherwise be misleading.
Still keeping the bpf_prog_run_xdp() is useful as it allows for grepping
in XDP supported drivers and to keep the typecheck on the context intact.
For mlx4, this means we don't have a double rcu_read_lock() anymore. nfp can
just make use of bpf_prog_run_xdp(), too. For qede, just move rcu_read_lock()
out of the helper. When the driver gets atomic replace support, this will
move to call-sites eventually.

mlx5 needs actual fixing as it has the same issue as described already in
326fe02d1e ("net/mlx4_en: protect ring->xdp_prog with rcu_read_lock"),
that is, we're under RCU bh at this time, BPF programs are released via
call_rcu(), and call_rcu() != call_rcu_bh(), so we need to properly mark
read side as programs can get xchg()'ed in mlx5e_xdp_set() without queue
reset.

Fixes: 86994156c7 ("net/mlx5e: XDP fast RX drop bpf programs support")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann
2016-11-30 22:16:06 +01:00
committed by David S. Miller
parent 83a1a1a70e
commit 366cbf2f46
4 changed files with 23 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
include/linux/filter.h
View File

@@ -498,16 +498,16 @@ static inline u32 bpf_prog_run_clear_cb(const struct bpf_prog *prog,
return BPF_PROG_RUN(prog, skb);
}
static inline u32 bpf_prog_run_xdp(const struct bpf_prog *prog,
struct xdp_buff *xdp)
static __always_inline u32 bpf_prog_run_xdp(const struct bpf_prog *prog,
struct xdp_buff *xdp)
{
u32 ret;
rcu_read_lock();
ret = BPF_PROG_RUN(prog, xdp);
rcu_read_unlock();
return ret;
/* Caller needs to hold rcu_read_lock() (!), otherwise program
* can be released while still running, or map elements could be
* freed early while still having concurrent users. XDP fastpath
* already takes rcu_read_lock() when fetching the program, so
* it's not necessary here anymore.
*/
return BPF_PROG_RUN(prog, xdp);
}
static inline unsigned int bpf_prog_size(unsigned int proglen)