* [PATCHv2] bpf: Take module reference for trampoline in module
@ 2021-03-24 17:40 Jiri Olsa
2021-03-25 21:26 ` Daniel Borkmann
0 siblings, 1 reply; 3+ messages in thread
From: Jiri Olsa @ 2021-03-24 17:40 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko
Cc: netdev, bpf, Martin KaFai Lau, Song Liu, Yonghong Song,
John Fastabend, KP Singh, Steven Rostedt
Currently module can be unloaded even if there's a trampoline
register in it. It's easily reproduced by running in parallel:
# while :; do ./test_progs -t module_attach; done
# while :; do rmmod bpf_testmod; sleep 0.5; done
Taking the module reference in case the trampoline's ip is
within the module code. Releasing it when the trampoline's
ip is unregistered.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
v2 changes:
- fixed ip_module_put to do preempt_disable/preempt_enable
kernel/bpf/trampoline.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 1f3a4be4b175..39e4280f94e4 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -87,6 +87,26 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
return tr;
}
+static struct module *ip_module_get(unsigned long ip)
+{
+ struct module *mod;
+ int err = 0;
+
+ preempt_disable();
+ mod = __module_text_address(ip);
+ if (mod && !try_module_get(mod))
+ err = -ENOENT;
+ preempt_enable();
+ return err ? ERR_PTR(err) : mod;
+}
+
+static void ip_module_put(unsigned long ip)
+{
+ preempt_disable();
+ module_put(__module_text_address(ip));
+ preempt_enable();
+}
+
static int is_ftrace_location(void *ip)
{
long addr;
@@ -108,6 +128,9 @@ static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
ret = unregister_ftrace_direct((long)ip, (long)old_addr);
else
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
+
+ if (!ret)
+ ip_module_put((unsigned long) ip);
return ret;
}
@@ -126,6 +149,7 @@ static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_ad
/* first time registering */
static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
{
+ struct module *mod;
void *ip = tr->func.addr;
int ret;
@@ -134,10 +158,17 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
return ret;
tr->func.ftrace_managed = ret;
+ mod = ip_module_get((unsigned long) ip);
+ if (IS_ERR(mod))
+ return -ENOENT;
+
if (tr->func.ftrace_managed)
ret = register_ftrace_direct((long)ip, (long)new_addr);
else
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
+
+ if (ret)
+ module_put(mod);
return ret;
}
--
2.30.2
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCHv2] bpf: Take module reference for trampoline in module
2021-03-24 17:40 [PATCHv2] bpf: Take module reference for trampoline in module Jiri Olsa
@ 2021-03-25 21:26 ` Daniel Borkmann
2021-03-25 21:39 ` Jiri Olsa
0 siblings, 1 reply; 3+ messages in thread
From: Daniel Borkmann @ 2021-03-25 21:26 UTC (permalink / raw)
To: Jiri Olsa, Alexei Starovoitov, Andrii Nakryiko
Cc: netdev, bpf, Martin KaFai Lau, Song Liu, Yonghong Song,
John Fastabend, KP Singh, Steven Rostedt
On 3/24/21 6:40 PM, Jiri Olsa wrote:
> Currently module can be unloaded even if there's a trampoline
> register in it. It's easily reproduced by running in parallel:
>
> # while :; do ./test_progs -t module_attach; done
> # while :; do rmmod bpf_testmod; sleep 0.5; done
>
> Taking the module reference in case the trampoline's ip is
> within the module code. Releasing it when the trampoline's
> ip is unregistered.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> v2 changes:
> - fixed ip_module_put to do preempt_disable/preempt_enable
>
> kernel/bpf/trampoline.c | 31 +++++++++++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> index 1f3a4be4b175..39e4280f94e4 100644
> --- a/kernel/bpf/trampoline.c
> +++ b/kernel/bpf/trampoline.c
> @@ -87,6 +87,26 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
> return tr;
> }
>
> +static struct module *ip_module_get(unsigned long ip)
> +{
> + struct module *mod;
> + int err = 0;
> +
> + preempt_disable();
> + mod = __module_text_address(ip);
> + if (mod && !try_module_get(mod))
> + err = -ENOENT;
> + preempt_enable();
> + return err ? ERR_PTR(err) : mod;
> +}
> +
> +static void ip_module_put(unsigned long ip)
> +{
> + preempt_disable();
> + module_put(__module_text_address(ip));
> + preempt_enable();
Could we cache the mod pointer in tr instead of doing another addr search
for dropping the ref?
> +}
> +
> static int is_ftrace_location(void *ip)
> {
> long addr;
> @@ -108,6 +128,9 @@ static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
> ret = unregister_ftrace_direct((long)ip, (long)old_addr);
> else
> ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
> +
> + if (!ret)
> + ip_module_put((unsigned long) ip);
> return ret;
> }
>
> @@ -126,6 +149,7 @@ static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_ad
> /* first time registering */
> static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
> {
> + struct module *mod;
> void *ip = tr->func.addr;
> int ret;
>
> @@ -134,10 +158,17 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
> return ret;
> tr->func.ftrace_managed = ret;
>
> + mod = ip_module_get((unsigned long) ip);
> + if (IS_ERR(mod))
> + return -ENOENT;
> +
> if (tr->func.ftrace_managed)
> ret = register_ftrace_direct((long)ip, (long)new_addr);
> else
> ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
> +
> + if (ret)
> + module_put(mod);
> return ret;
> }
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCHv2] bpf: Take module reference for trampoline in module
2021-03-25 21:26 ` Daniel Borkmann
@ 2021-03-25 21:39 ` Jiri Olsa
0 siblings, 0 replies; 3+ messages in thread
From: Jiri Olsa @ 2021-03-25 21:39 UTC (permalink / raw)
To: Daniel Borkmann
Cc: Jiri Olsa, Alexei Starovoitov, Andrii Nakryiko, netdev, bpf,
Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
KP Singh, Steven Rostedt
On Thu, Mar 25, 2021 at 10:26:32PM +0100, Daniel Borkmann wrote:
> On 3/24/21 6:40 PM, Jiri Olsa wrote:
> > Currently module can be unloaded even if there's a trampoline
> > register in it. It's easily reproduced by running in parallel:
> >
> > # while :; do ./test_progs -t module_attach; done
> > # while :; do rmmod bpf_testmod; sleep 0.5; done
> >
> > Taking the module reference in case the trampoline's ip is
> > within the module code. Releasing it when the trampoline's
> > ip is unregistered.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> > v2 changes:
> > - fixed ip_module_put to do preempt_disable/preempt_enable
> >
> > kernel/bpf/trampoline.c | 31 +++++++++++++++++++++++++++++++
> > 1 file changed, 31 insertions(+)
> >
> > diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> > index 1f3a4be4b175..39e4280f94e4 100644
> > --- a/kernel/bpf/trampoline.c
> > +++ b/kernel/bpf/trampoline.c
> > @@ -87,6 +87,26 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
> > return tr;
> > }
> > +static struct module *ip_module_get(unsigned long ip)
> > +{
> > + struct module *mod;
> > + int err = 0;
> > +
> > + preempt_disable();
> > + mod = __module_text_address(ip);
> > + if (mod && !try_module_get(mod))
> > + err = -ENOENT;
> > + preempt_enable();
> > + return err ? ERR_PTR(err) : mod;
> > +}
> > +
> > +static void ip_module_put(unsigned long ip)
> > +{
> > + preempt_disable();
> > + module_put(__module_text_address(ip));
> > + preempt_enable();
>
> Could we cache the mod pointer in tr instead of doing another addr search
> for dropping the ref?
right.. I moved it from the ftrace layer where this was not an option,
so I did not realize bpf_trampoline could get extended, will send new
version
thanks,
jirka
>
> > +}
> > +
> > static int is_ftrace_location(void *ip)
> > {
> > long addr;
> > @@ -108,6 +128,9 @@ static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
> > ret = unregister_ftrace_direct((long)ip, (long)old_addr);
> > else
> > ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
> > +
> > + if (!ret)
> > + ip_module_put((unsigned long) ip);
> > return ret;
> > }
> > @@ -126,6 +149,7 @@ static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_ad
> > /* first time registering */
> > static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
> > {
> > + struct module *mod;
> > void *ip = tr->func.addr;
> > int ret;
> > @@ -134,10 +158,17 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
> > return ret;
> > tr->func.ftrace_managed = ret;
> > + mod = ip_module_get((unsigned long) ip);
> > + if (IS_ERR(mod))
> > + return -ENOENT;
> > +
> > if (tr->func.ftrace_managed)
> > ret = register_ftrace_direct((long)ip, (long)new_addr);
> > else
> > ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
> > +
> > + if (ret)
> > + module_put(mod);
> > return ret;
> > }
> >
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-03-24 17:40 [PATCHv2] bpf: Take module reference for trampoline in module Jiri Olsa
2021-03-25 21:26 ` Daniel Borkmann
2021-03-25 21:39 ` Jiri Olsa
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