[PATCH] ftrace: Fix use-after-free issue in ftrace_location()
From: Zheng Yejian <hidden>
Date: 2024-04-01 12:55:16
Also in:
lkml
Subsystem:
function hooks (ftrace), the rest, tracing · Maintainers:
Steven Rostedt, Masami Hiramatsu, Linus Torvalds
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+ #213
[...]
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 when lookup_rec() is lookuping ftrace record of
an address in some module, and at the same time in ftrace_release_mod(),
the memory that saving ftrace records has been freed as that module is
being deleted.
register_kprobes() {
check_kprobe_address_safe() {
arch_check_ftrace_location() {
ftrace_location() {
lookup_rec() // access memory that has been freed by
// ftrace_release_mod() !!!
It seems that the ftrace_lock is required when lookuping records in
ftrace_location(), so is ftrace_location_range().
Fixes: ae6aa16fdc16 ("kprobes: introduce ftrace based optimization")
Signed-off-by: Zheng Yejian <redacted>
---
kernel/trace/ftrace.c | 28 ++++++++++++++++++----------
1 file changed, 18 insertions(+), 10 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index da1710499698..838d175709c1 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c@@ -1581,7 +1581,7 @@ static struct dyn_ftrace *lookup_rec(unsigned long start, unsigned long end) } /** - * ftrace_location_range - return the first address of a traced location + * ftrace_location_range_locked - return the first address of a traced location * if it touches the given ip range * @start: start of range to search. * @end: end of range to search (inclusive). @end points to the last byte
@@ -1592,7 +1592,7 @@ static struct dyn_ftrace *lookup_rec(unsigned long start, unsigned long end) * that is either a NOP or call to the function tracer. It checks the ftrace * internal tables to determine if the address belongs or not. */ -unsigned long ftrace_location_range(unsigned long start, unsigned long end) +static unsigned long ftrace_location_range_locked(unsigned long start, unsigned long end) { struct dyn_ftrace *rec;
@@ -1603,6 +1603,17 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end) return 0; } +unsigned long ftrace_location_range(unsigned long start, unsigned long end) +{ + unsigned long loc; + + mutex_lock(&ftrace_lock); + loc = ftrace_location_range_locked(start, end); + mutex_unlock(&ftrace_lock); + + return loc; +} + /** * ftrace_location - return the ftrace location * @ip: the instruction pointer to check
@@ -1614,25 +1625,22 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end) */ unsigned long ftrace_location(unsigned long ip) { - struct dyn_ftrace *rec; + unsigned long loc; unsigned long offset; unsigned long size; - rec = lookup_rec(ip, ip); - if (!rec) { + loc = ftrace_location_range(ip, ip); + if (!loc) { if (!kallsyms_lookup_size_offset(ip, &size, &offset)) goto out; /* map sym+0 to __fentry__ */ if (!offset) - rec = lookup_rec(ip, ip + size - 1); + loc = ftrace_location_range(ip, ip + size - 1); } - if (rec) - return rec->ip; - out: - return 0; + return loc; } /**
--
2.25.1