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fprobe: make fprobe_kprobe_handler recursion free

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Current implementation calls kprobe related functions before doing
ftrace recursion check in fprobe_kprobe_handler, which opens door
to kernel crash due to stack recursion if preempt_count_{add, sub}
is traceable in kprobe_busy_{begin, end}.

Things goes like this without this patch quoted from Steven:
"
fprobe_kprobe_handler() {
   kprobe_busy_begin() {
      preempt_disable() {
         preempt_count_add() {  <-- trace
            fprobe_kprobe_handler() {
		[ wash, rinse, repeat, CRASH!!! ]
"

By refactoring the common part out of fprobe_kprobe_handler and
fprobe_handler and call ftrace recursion detection at the very beginning,
the whole fprobe_kprobe_handler is free from recursion.

[ Fix the indentation of __fprobe_handler() parameters. ]

Link: https://lore.kernel.org/all/20230517034510.15639-3-zegao@tencent.com/

Fixes: ab51e15d53 ("fprobe: Introduce FPROBE_FL_KPROBE_SHARED flag for fprobe")
Signed-off-by: Ze Gao <zegao@tencent.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
This commit is contained in:
Ze Gao 2023-05-17 11:45:07 +08:00 committed by Masami Hiramatsu (Google)
parent be243bacfb
commit 3cc4e2c5fb
1 changed files with 44 additions and 15 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

57
kernel/trace/fprobe.c
View file

@ -20,30 +20,22 @@ struct fprobe_rethook_node {
char data[];
};
static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
static inline void __fprobe_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
struct fprobe_rethook_node *fpr;
struct rethook_node *rh = NULL;
struct fprobe *fp;
void *entry_data = NULL;
int bit, ret = 0;
int ret = 0;
fp = container_of(ops, struct fprobe, ops);
if (fprobe_disabled(fp))
return;
bit = ftrace_test_recursion_trylock(ip, parent_ip);
if (bit < 0) {
fp->nmissed++;
return;
}
if (fp->exit_handler) {
rh = rethook_try_get(fp->rethook);
if (!rh) {
fp->nmissed++;
goto out;
return;
}
fpr = container_of(rh, struct fprobe_rethook_node, node);
fpr->entry_ip = ip;
@ -61,23 +53,60 @@ static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
else
rethook_hook(rh, ftrace_get_regs(fregs), true);
}
out:
}
static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
struct fprobe *fp;
int bit;
fp = container_of(ops, struct fprobe, ops);
if (fprobe_disabled(fp))
return;
/* recursion detection has to go before any traceable function and
* all functions before this point should be marked as notrace
*/
bit = ftrace_test_recursion_trylock(ip, parent_ip);
if (bit < 0) {
fp->nmissed++;
return;
}
__fprobe_handler(ip, parent_ip, ops, fregs);
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(fprobe_handler);
static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
struct fprobe *fp = container_of(ops, struct fprobe, ops);
struct fprobe *fp;
int bit;
fp = container_of(ops, struct fprobe, ops);
if (fprobe_disabled(fp))
return;
/* recursion detection has to go before any traceable function and
* all functions called before this point should be marked as notrace
*/
bit = ftrace_test_recursion_trylock(ip, parent_ip);
if (bit < 0) {
fp->nmissed++;
return;
}
if (unlikely(kprobe_running())) {
fp->nmissed++;
return;
}
kprobe_busy_begin();
fprobe_handler(ip, parent_ip, ops, fregs);
__fprobe_handler(ip, parent_ip, ops, fregs);
kprobe_busy_end();
ftrace_test_recursion_unlock(bit);
}
static void fprobe_exit_handler(struct rethook_node *rh, void *data,