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authorJiri Olsa <jolsa@kernel.org>2021-03-26 11:59:00 +0100
committerAlexei Starovoitov <ast@kernel.org>2021-03-26 19:30:11 -0700
commit861de02e5f3f2a104eecc5af1d248cb7bf8c5f75 (patch)
tree79748704faea37470f54bdef1658b9505d057f86 /kernel
parentd6fe1cf89026d3111112ee29ef8d93cd7a8aaa24 (diff)
downloadlinux-861de02e5f3f2a104eecc5af1d248cb7bf8c5f75.tar.bz2
bpf: Take module reference for trampoline in module
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> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20210326105900.151466-1-jolsa@kernel.org
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/trampoline.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 1f3a4be4b175..4aa8b52adf25 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -9,6 +9,7 @@
#include <linux/btf.h>
#include <linux/rcupdate_trace.h>
#include <linux/rcupdate_wait.h>
+#include <linux/module.h>
/* dummy _ops. The verifier will operate on target program's ops. */
const struct bpf_verifier_ops bpf_extension_verifier_ops = {
@@ -87,6 +88,26 @@ out:
return tr;
}
+static int bpf_trampoline_module_get(struct bpf_trampoline *tr)
+{
+ struct module *mod;
+ int err = 0;
+
+ preempt_disable();
+ mod = __module_text_address((unsigned long) tr->func.addr);
+ if (mod && !try_module_get(mod))
+ err = -ENOENT;
+ preempt_enable();
+ tr->mod = mod;
+ return err;
+}
+
+static void bpf_trampoline_module_put(struct bpf_trampoline *tr)
+{
+ module_put(tr->mod);
+ tr->mod = NULL;
+}
+
static int is_ftrace_location(void *ip)
{
long addr;
@@ -108,6 +129,9 @@ 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)
+ bpf_trampoline_module_put(tr);
return ret;
}
@@ -134,10 +158,16 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
return ret;
tr->func.ftrace_managed = ret;
+ if (bpf_trampoline_module_get(tr))
+ 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)
+ bpf_trampoline_module_put(tr);
return ret;
}