On Mon, Nov 11, 2024 at 02:44:45PM +0000, Hagar Hemdan wrote:
From: Zheng Yejian zhengyejian1@huawei.com
commit e60b613df8b6253def41215402f72986fee3fc8d upstream.
KASAN reports a bug:
BUG: KASAN: use-after-free in ftrace_location+0x90/0x120 Read of size 8 at addr ffff888141d40010 by task insmod/424 CPU: 8 PID: 424 Comm: insmod Tainted: G W 6.9.0-rc2+ [...] Call Trace:
<TASK> dump_stack_lvl+0x68/0xa0 print_report+0xcf/0x610 kasan_report+0xb5/0xe0 ftrace_location+0x90/0x120 register_kprobe+0x14b/0xa40 kprobe_init+0x2d/0xff0 [kprobe_example] do_one_initcall+0x8f/0x2d0 do_init_module+0x13a/0x3c0 load_module+0x3082/0x33d0 init_module_from_file+0xd2/0x130 __x64_sys_finit_module+0x306/0x440 do_syscall_64+0x68/0x140 entry_SYSCALL_64_after_hwframe+0x71/0x79
The root cause is that, in ftrace_location_range(), ftrace record of some address is being searched in ftrace pages of some module, but those ftrace pages at the same time is being freed in ftrace_release_mod() as the corresponding module is being deleted:
CPU1 | CPU2register_kprobes() { | delete_module() { check_kprobe_address_safe() { | arch_check_ftrace_location() { | ftrace_location() { | lookup_rec() // USE! | ftrace_release_mod() // Free!
To fix this issue:
- Hold rcu lock as accessing ftrace pages in ftrace_location_range();
- Use ftrace_location_range() instead of lookup_rec() in ftrace_location();
- Call synchronize_rcu() before freeing any ftrace pages both in ftrace_process_locs()/ftrace_release_mod()/ftrace_free_mem().
Link: https://lore.kernel.org/linux-trace-kernel/20240509192859.1273558-1-zhengyej...
Cc: stable@vger.kernel.org Cc: mhiramat@kernel.org Cc: mark.rutland@arm.com Cc: mathieu.desnoyers@efficios.com Fixes: ae6aa16fdc16 ("kprobes: introduce ftrace based optimization") Suggested-by: Steven Rostedt rostedt@goodmis.org Signed-off-by: Zheng Yejian zhengyejian1@huawei.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org [Hagar: Modified to apply on v5.4.y] Signed-off-by: Hagar Hemdan hagarhem@amazon.com
only compile tested.
kernel/trace/ftrace.c | 30 +++++++++++++++++++++--------- 1 file changed, 21 insertions(+), 9 deletions(-)
Now queued up, thanks.
greg k-h