bpf: Fix map poke update #6072
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bpf: Fix map poke update #6072
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Upstream branch: dfce9cb |
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=806372 expired. Closing PR. |
Lee pointed out issue found by syscaller [0] hitting BUG in prog array
map poke update in prog_array_map_poke_run function due to error value
returned from bpf_arch_text_poke function.
There's race window where bpf_arch_text_poke can fail due to missing
bpf program kallsym symbols, which is accounted for with check for
-EINVAL in that BUG_ON call.
The problem is that in such case we won't update the tail call jump
and cause imbalance for the next tail call update check which will
fail with -EBUSY in bpf_arch_text_poke.
I'm hitting following race during the program load:
CPU 0 CPU 1
bpf_prog_load
bpf_check
do_misc_fixups
prog_array_map_poke_track
map_update_elem
bpf_fd_array_map_update_elem
prog_array_map_poke_run
bpf_arch_text_poke returns -EINVAL
bpf_prog_kallsyms_add
After bpf_arch_text_poke (CPU 1) fails to update the tail call jump, the next
poke update fails on expected jump instruction check in bpf_arch_text_poke
with -EBUSY and triggers the BUG_ON in prog_array_map_poke_run.
Similar race exists on the program unload.
Fixing this by moving the update to bpf_arch_poke_desc_update function which
makes sure we call __bpf_arch_text_poke that skips the bpf address check.
Each architecture has slightly different approach wrt looking up bpf address
in bpf_arch_text_poke, so instead of splitting the function or adding new
'checkip' argument in previous version, it seems best to move the whole
map_poke_run update as arch specific code.
[0] https://syzkaller.appspot.com/bug?extid=97a4fe20470e9bc30810
Cc: Lee Jones <lee@kernel.org>
Cc: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Fixes: ebf7d1f ("bpf, x64: rework pro/epilogue and tailcall handling in JIT")
Reported-by: syzbot+97a4fe20470e9bc30810@syzkaller.appspotmail.com
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Adding test that tries to trigger the BUG_IN during early map update in prog_array_map_poke_run function. The idea is to share prog array map between thread that constantly updates it and another one loading a program that uses that prog array. Eventually we will hit a place where the program is ok to be updated (poke->tailcall_target_stable check) but the address is still not registered in kallsyms, so the bpf_arch_text_poke returns -EINVAL and cause imbalance for the next tail call update check, which will fail with -EBUSY in bpf_arch_text_poke as described in previous fix. Acked-by: Ilya Leoshkevich <iii@linux.ibm.com> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=807313 irrelevant now. Closing PR. |
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Pull request for series with
subject: bpf: Fix map poke update
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=806372