799a914e48
[ Upstream commit b8e3a87a627b575896e448021e5c2f8a3bc19931 ]
Currently get_perf_callchain only supports user stack walking for
the current task. Passing the correct *crosstask* param will return
0 frames if the task passed to __bpf_get_stack isn't the current
one instead of a single incorrect frame/address. This change
passes the correct *crosstask* param but also does a preemptive
check in __bpf_get_stack if the task is current and returns
-EOPNOTSUPP if it is not.
This issue was found using bpf_get_task_stack inside a BPF
iterator ("iter/task"), which iterates over all tasks.
bpf_get_task_stack works fine for fetching kernel stacks
but because get_perf_callchain relies on the caller to know
if the requested *task* is the current one (via *crosstask*)
it was failing in a confusing way.
It might be possible to get user stacks for all tasks utilizing
something like access_process_vm but that requires the bpf
program calling bpf_get_task_stack to be sleepable and would
therefore be a breaking change.
Fixes:
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||
|---|---|---|
| .. | ||
| tc_act | ||
| bpf.h | ||
| bpf_common.h | ||
| bpf_perf_event.h | ||
| btf.h | ||
| const.h | ||
| erspan.h | ||
| ethtool.h | ||
| fadvise.h | ||
| fcntl.h | ||
| filter.h | ||
| fs.h | ||
| fscrypt.h | ||
| hw_breakpoint.h | ||
| if_link.h | ||
| if_tun.h | ||
| if_xdp.h | ||
| in.h | ||
| kcmp.h | ||
| kvm.h | ||
| mman.h | ||
| mount.h | ||
| netlink.h | ||
| openat2.h | ||
| perf_event.h | ||
| pkt_cls.h | ||
| pkt_sched.h | ||
| prctl.h | ||
| sched.h | ||
| seg6.h | ||
| seg6_local.h | ||
| stat.h | ||
| stddef.h | ||
| tcp.h | ||
| tls.h | ||
| types.h | ||
| usbdevice_fs.h | ||
| vhost.h | ||