On Mon, Nov 11, 2024 at 02:44:45PM +0000, Hagar Hemdan wrote: > From: Zheng Yejian <zhengyejian1@xxxxxxxxxx> > > 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 | CPU2 > register_kprobes() { | delete_module() { > check_kprobe_address_safe() { | > arch_check_ftrace_location() { | > ftrace_location() { | > lookup_rec() // USE! | ftrace_release_mod() // Free! > > To fix this issue: > 1. Hold rcu lock as accessing ftrace pages in ftrace_location_range(); > 2. Use ftrace_location_range() instead of lookup_rec() in > ftrace_location(); > 3. 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-zhengyejian1@xxxxxxxxxx > > Cc: stable@xxxxxxxxxxxxxxx > Cc: <mhiramat@xxxxxxxxxx> > Cc: <mark.rutland@xxxxxxx> > Cc: <mathieu.desnoyers@xxxxxxxxxxxx> > Fixes: ae6aa16fdc16 ("kprobes: introduce ftrace based optimization") > Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx> > Signed-off-by: Zheng Yejian <zhengyejian1@xxxxxxxxxx> > Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> > [Hagar: Modified to apply on v5.4.y] > Signed-off-by: Hagar Hemdan <hagarhem@xxxxxxxxxx> > --- > only compile tested. > --- > kernel/trace/ftrace.c | 30 +++++++++++++++++++++--------- > 1 file changed, 21 insertions(+), 9 deletions(-) Now queued up, thanks. greg k-h