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bpf: put uprobe link's path and task in release callback

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There is no need to delay putting either path or task to deallocation
step. It can be done right after bpf_uprobe_unregister. Between release
and dealloc, there could be still some running BPF programs, but they
don't access either task or path, only data in link->uprobes, so it is
safe to do.

On the other hand, doing path_put() in dealloc callback makes this
dealloc sleepable because path_put() itself might sleep. Which is
problematic due to the need to call uprobe's dealloc through call_rcu(),
which is what is done in the next bug fix patch. So solve the problem by
releasing these resources early.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240328052426.3042617-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2024-03-27 22:24:25 -07:00 committed by Alexei Starovoitov
parent 037965402a
commit e9c856cabe
1 changed files with 3 additions and 3 deletions
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6
kernel/trace/bpf_trace.c
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@ -3157,6 +3157,9 @@ static void bpf_uprobe_multi_link_release(struct bpf_link *link)
umulti_link = container_of(link, struct bpf_uprobe_multi_link, link); umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
bpf_uprobe_unregister(&umulti_link->path, umulti_link->uprobes, umulti_link->cnt); bpf_uprobe_unregister(&umulti_link->path, umulti_link->uprobes, umulti_link->cnt);
if (umulti_link->task)
put_task_struct(umulti_link->task);
path_put(&umulti_link->path);
} }
static void bpf_uprobe_multi_link_dealloc(struct bpf_link *link) static void bpf_uprobe_multi_link_dealloc(struct bpf_link *link)
@ -3164,9 +3167,6 @@ static void bpf_uprobe_multi_link_dealloc(struct bpf_link *link)
struct bpf_uprobe_multi_link *umulti_link; struct bpf_uprobe_multi_link *umulti_link;
umulti_link = container_of(link, struct bpf_uprobe_multi_link, link); umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
if (umulti_link->task)
put_task_struct(umulti_link->task);
path_put(&umulti_link->path);
kvfree(umulti_link->uprobes); kvfree(umulti_link->uprobes);
kfree(umulti_link); kfree(umulti_link);
} }