On 12/15/22 1:44 PM, Jiri Olsa wrote:
Currently we always cleanup/decrement bpf_bprintf_nest_level
variable in bpf_bprintf_cleanup if it's > 0.
There's possible scenario where this could cause a problem,
when bpf_bprintf_prepare does not get bin_args buffer (because
num_args is 0) and following bpf_bprintf_cleanup call decrements
bpf_bprintf_nest_level variable, like:
in task context:
bpf_bprintf_prepare(num_args != 0) increments 'bpf_bprintf_nest_level = 1'
-> first irq :
bpf_bprintf_prepare(num_args == 0)
bpf_bprintf_cleanup decrements 'bpf_bprintf_nest_level = 0'
-> second irq:
bpf_bprintf_prepare(num_args != 0) bpf_bprintf_nest_level = 1
gets same buffer as task context above
Adding check to bpf_bprintf_cleanup and doing the real cleanup
only if we got bin_args data in the first place.
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Acked-by: Yonghong Song <yhs@xxxxxx>
