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bpf: ensure RCU Tasks Trace GP for sleepable raw tracepoint BPF links

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Now that kernel supports sleepable tracepoints, the fact that
bpf_probe_unregister() is asynchronous, i.e., that it doesn't wait for
any in-flight tracepoints to conclude before returning, we now need to
delay BPF raw tp link's deallocation and bpf_prog_put() of its
underlying BPF program (regardless of program's own sleepable semantics)
until after full RCU Tasks Trace GP. With that GP over, we'll have
a guarantee that no tracepoint can reach BPF link and thus its BPF program.

We use newly added tracepoint_is_faultable() check to know when this RCU
Tasks Trace GP is necessary and utilize BPF link's own sleepable flag
passed through bpf_link_init_sleepable() initializer.

Link: https://lore.kernel.org/20241101181754.782341-3-andrii@kernel.org
Tested-by: Jordan Rife <jrife@google.com>
Reported-by: Jordan Rife <jrife@google.com>
Fixes: a363d27cdbc2 ("tracing: Allow system call tracepoints to handle page faults")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Andrii Nakryiko 2024-11-01 11:17:54 -07:00 committed by Steven Rostedt (Google)
parent 61c6fefa92
commit 24507ce81e
1 changed files with 4 additions and 2 deletions
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6
kernel/bpf/syscall.c
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@ -35,6 +35,7 @@
#include <linux/rcupdate_trace.h>
#include <linux/memcontrol.h>
#include <linux/trace_events.h>
#include <linux/tracepoint.h>
#include <net/netfilter/nf_bpf_link.h>
#include <net/netkit.h>
@ -3845,8 +3846,9 @@ static int bpf_raw_tp_link_attach(struct bpf_prog *prog,
err = -ENOMEM;
goto out_put_btp;
}
bpf_link_init(&link->link, BPF_LINK_TYPE_RAW_TRACEPOINT,
&bpf_raw_tp_link_lops, prog);
bpf_link_init_sleepable(&link->link, BPF_LINK_TYPE_RAW_TRACEPOINT,
&bpf_raw_tp_link_lops, prog,
tracepoint_is_faultable(btp->tp));
link->btp = btp;
link->cookie = cookie;