[PATCH 5.19 0492/1157] bpf, x86: fix freeing of not-finalized bpf_prog_pack

Greg Kroah-Hartman
2022-08-15T23:56:47Z

From: Song Liu <song@kernel.org>

[ Upstream commit 1d5f82d9dd477d5c66e0214a68c3e4f308eadd6d ]

syzbot reported a few issues with bpf_prog_pack [1], [2]. This only happens
with multiple subprogs. In jit_subprogs(), we first call bpf_int_jit_compile()
on each sub program. And then, we call it on each sub program again. jit_data
is not freed in the first call of bpf_int_jit_compile(). Similarly we don't
call bpf_jit_binary_pack_finalize() in the first call of bpf_int_jit_compile().

If bpf_int_jit_compile() failed for one sub program, we will call
bpf_jit_binary_pack_finalize() for this sub program. However, we don't have a
chance to call it for other sub programs. Then we will hit "goto out_free" in
jit_subprogs(), and call bpf_jit_free on some subprograms that haven't got
bpf_jit_binary_pack_finalize() yet.

At this point, bpf_jit_binary_pack_free() is called and the whole 2MB page is
freed erroneously.

Fix this with a custom bpf_jit_free() for x86_64, which calls
bpf_jit_binary_pack_finalize() if necessary. Also, with custom
bpf_jit_free(), bpf_prog_aux->use_bpf_prog_pack is not needed any more,
remove it.

Fixes: 1022a5498f6f ("bpf, x86_64: Use bpf_jit_binary_pack_alloc")
[1] https://syzkaller.appspot.com/bug?extid=2f649ec6d2eea1495a8f
[2] https://syzkaller.appspot.com/bug?extid=87f65c75f4a72db05445
Reported-by: syzbot+2f649ec6d2eea1495a8f@syzkaller.appspotmail.com
Reported-by: syzbot+87f65c75f4a72db05445@syzkaller.appspotmail.com
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20220706002612.4013790-1-song@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/net/bpf_jit_comp.c | 25 +++++++++++++++++++++++++
include/linux/bpf.h | 1 -
include/linux/filter.h | 8 ++++++++
kernel/bpf/core.c | 29 ++++++++++++-----------------
4 files changed, 45 insertions(+), 18 deletions(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index eba704b9ce1e..41d170653e8d 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -2512,3 +2512,28 @@ bool bpf_jit_supports_subprog_tailcalls(void)
{
return true;
}
+
+void bpf_jit_free(struct bpf_prog *prog)
+{
+ if (prog->jited) {
+ struct x64_jit_data *jit_data = prog->aux->jit_data;
+ struct bpf_binary_header *hdr;
+
+ /*
+ * If we fail the final pass of JIT (from jit_subprogs),
+ * the program may not be finalized yet. Call finalize here
+ * before freeing it.
+ */
+ if (jit_data) {
+ bpf_jit_binary_pack_finalize(prog, jit_data->header,
+ jit_data->rw_header);
+ kvfree(jit_data->addrs);
+ kfree(jit_data);
+ }
+ hdr = bpf_jit_binary_pack_hdr(prog);
+ bpf_jit_binary_pack_free(hdr, NULL);
+ WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog));
+ }
+
+ bpf_prog_unlock_free(prog);
+}
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2b914a56a2c5..7424cf234ae0 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1025,7 +1025,6 @@ struct bpf_prog_aux {
bool sleepable;
bool tail_call_reachable;
bool xdp_has_frags;
- bool use_bpf_prog_pack;
/* BTF_KIND_FUNC_PROTO for valid attach_btf_id */
const struct btf_type *attach_func_proto;
/* function name for valid attach_btf_id */
diff --git a/include/linux/filter.h b/include/linux/filter.h
index d9a0db845b50..8fd2e2f58eeb 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1061,6 +1061,14 @@ u64 bpf_jit_alloc_exec_limit(void);
void *bpf_jit_alloc_exec(unsigned long size);
void bpf_jit_free_exec(void *addr);
void bpf_jit_free(struct bpf_prog *fp);
+struct bpf_binary_header *
+bpf_jit_binary_pack_hdr(const struct bpf_prog *fp);
+
+static inline bool bpf_prog_kallsyms_verify_off(const struct bpf_prog *fp)
+{
+ return list_empty(&fp->aux->ksym.lnode) ||
+ fp->aux->ksym.lnode.prev == LIST_POISON2;
+}

struct bpf_binary_header *
bpf_jit_binary_pack_alloc(unsigned int proglen, u8 **ro_image,
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 6e3fe4b7230b..fb6bd57228a8 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -649,12 +649,6 @@ static bool bpf_prog_kallsyms_candidate(const struct bpf_prog *fp)
return fp->jited && !bpf_prog_was_classic(fp);
}

-static bool bpf_prog_kallsyms_verify_off(const struct bpf_prog *fp)
-{
- return list_empty(&fp->aux->ksym.lnode) ||
- fp->aux->ksym.lnode.prev == LIST_POISON2;
-}
-
void bpf_prog_kallsyms_add(struct bpf_prog *fp)
{
if (!bpf_prog_kallsyms_candidate(fp) ||
@@ -1152,7 +1146,6 @@ int bpf_jit_binary_pack_finalize(struct bpf_prog *prog,
bpf_prog_pack_free(ro_header);
return PTR_ERR(ptr);
}
- prog->aux->use_bpf_prog_pack = true;
return 0;
}

@@ -1176,17 +1169,23 @@ void bpf_jit_binary_pack_free(struct bpf_binary_header *ro_header,
bpf_jit_uncharge_modmem(size);
}

+struct bpf_binary_header *
+bpf_jit_binary_pack_hdr(const struct bpf_prog *fp)
+{
+ unsigned long real_start = (unsigned long)fp->bpf_func;
+ unsigned long addr;
+
+ addr = real_start & BPF_PROG_CHUNK_MASK;
+ return (void *)addr;
+}
+
static inline struct bpf_binary_header *
bpf_jit_binary_hdr(const struct bpf_prog *fp)
{
unsigned long real_start = (unsigned long)fp->bpf_func;
unsigned long addr;

- if (fp->aux->use_bpf_prog_pack)
- addr = real_start & BPF_PROG_CHUNK_MASK;
- else
- addr = real_start & PAGE_MASK;
-
+ addr = real_start & PAGE_MASK;
return (void *)addr;
}

@@ -1199,11 +1198,7 @@ void __weak bpf_jit_free(struct bpf_prog *fp)
if (fp->jited) {
struct bpf_binary_header *hdr = bpf_jit_binary_hdr(fp);

- if (fp->aux->use_bpf_prog_pack)
- bpf_jit_binary_pack_free(hdr, NULL /* rw_buffer */);
- else
- bpf_jit_binary_free(hdr);
-
+ bpf_jit_binary_free(hdr);
WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(fp));
}

--
2.35.1