tracing: fprobe: fix suspicious rcu usage in fprobe_entry
rcu_read_lock() is not needed in fprobe_entry, but rcu_dereference_check()
is used in rhltable_lookup(), which causes suspicious RCU usage warning:
WARNING: suspicious RCU usage
6.17.0-rc1-00001-gdfe0d675df82 #1 Tainted: G S
-----------------------------
include/linux/rhashtable.h:602 suspicious rcu_dereference_check() usage!
......
stack backtrace:
CPU: 1 UID: 0 PID: 4652 Comm: ftracetest Tainted: G S
Tainted: [S]=CPU_OUT_OF_SPEC, [I]=FIRMWARE_WORKAROUND
Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.1.1 10/07/2015
Call Trace:
<TASK>
dump_stack_lvl+0x7c/0x90
lockdep_rcu_suspicious+0x14f/0x1c0
__rhashtable_lookup+0x1e0/0x260
? __pfx_kernel_clone+0x10/0x10
fprobe_entry+0x9a/0x450
? __lock_acquire+0x6b0/0xca0
? find_held_lock+0x2b/0x80
? __pfx_fprobe_entry+0x10/0x10
? __pfx_kernel_clone+0x10/0x10
? lock_acquire+0x14c/0x2d0
? __might_fault+0x74/0xc0
function_graph_enter_regs+0x2a0/0x550
? __do_sys_clone+0xb5/0x100
? __pfx_function_graph_enter_regs+0x10/0x10
? _copy_to_user+0x58/0x70
? __pfx_kernel_clone+0x10/0x10
? __x64_sys_rt_sigprocmask+0x114/0x180
? __pfx___x64_sys_rt_sigprocmask+0x10/0x10
? __pfx_kernel_clone+0x10/0x10
ftrace_graph_func+0x87/0xb0
As we discussed in [1], fix this by using guard(rcu)() in fprobe_entry()
to protect the rhltable_lookup() and rhl_for_each_entry_rcu() with
rcu_read_lock and suppress this warning.
Link: https://lore.kernel.org/all/20250904062729.151931-1-dongml2@chinatelecom.cn/
Link: https://lore.kernel.org/all/20250829021436.19982-1-dongml2@chinatelecom.cn/ [1]
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202508281655.54c87330-lkp@intel.com
Fixes: dfe0d675df82 ("tracing: fprobe: use rhltable for fprobe_ip_table")
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
1 file changed
