This is a note to let you know that I've just added the patch titled ftrace: Fix invalid address access in lookup_rec() when index is 0 to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ftrace-fix-invalid-address-access-in-lookup_rec-when-index-is-0.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From ee92fa443358f4fc0017c1d0d325c27b37802504 Mon Sep 17 00:00:00 2001 From: Chen Zhongjin <chenzhongjin@xxxxxxxxxx> Date: Thu, 9 Mar 2023 16:02:30 +0800 Subject: ftrace: Fix invalid address access in lookup_rec() when index is 0 From: Chen Zhongjin <chenzhongjin@xxxxxxxxxx> commit ee92fa443358f4fc0017c1d0d325c27b37802504 upstream. KASAN reported follow problem: BUG: KASAN: use-after-free in lookup_rec Read of size 8 at addr ffff000199270ff0 by task modprobe CPU: 2 Comm: modprobe Call trace: kasan_report __asan_load8 lookup_rec ftrace_location arch_check_ftrace_location check_kprobe_address_safe register_kprobe When checking pg->records[pg->index - 1].ip in lookup_rec(), it can get a pg which is newly added to ftrace_pages_start in ftrace_process_locs(). Before the first pg->index++, index is 0 and accessing pg->records[-1].ip will cause this problem. Don't check the ip when pg->index is 0. Link: https://lore.kernel.org/linux-trace-kernel/20230309080230.36064-1-chenzhongjin@xxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Fixes: 9644302e3315 ("ftrace: Speed up search by skipping pages by address") Suggested-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> Signed-off-by: Chen Zhongjin <chenzhongjin@xxxxxxxxxx> Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/trace/ftrace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1581,7 +1581,8 @@ unsigned long ftrace_location_range(unsi key.flags = end; /* overload flags, as it is unsigned long */ for (pg = ftrace_pages_start; pg; pg = pg->next) { - if (end < pg->records[0].ip || + if (pg->index == 0 || + end < pg->records[0].ip || start >= (pg->records[pg->index - 1].ip + MCOUNT_INSN_SIZE)) continue; rec = bsearch(&key, pg->records, pg->index, Patches currently in stable-queue which might be from chenzhongjin@xxxxxxxxxx are queue-4.19/ftrace-fix-invalid-address-access-in-lookup_rec-when-index-is-0.patch