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Date: Fri, 15 Mar 2024 15:34:29 +0100
From: Daniel Borkmann <daniel@...earbox.net>
To: Christophe Leroy <christophe.leroy@...roup.eu>,
"David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>,
Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman
<eddyz87@...il.com>, Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH bpf-next v2] bpf: Check return from set_memory_rox() and
friends
On 2/21/24 3:45 PM, Christophe Leroy wrote:
> arch_protect_bpf_trampoline() and alloc_new_pack() call
> set_memory_rox() which can fail, leading to unprotected memory.
>
> Take into account return from set_memory_XX() functions and add
> __must_check flag to arch_protect_bpf_trampoline().
>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> ---
> v2:
> - Move list_add_tail(&pack->list, &pack_list) at the end of alloc_new_pack()
> - Split 2 lines that are reported longer than 80 chars by BPF patchwork's checkpatch report.
> ---
> arch/x86/net/bpf_jit_comp.c | 6 ++++--
> include/linux/bpf.h | 4 ++--
> kernel/bpf/bpf_struct_ops.c | 9 +++++++--
> kernel/bpf/core.c | 29 ++++++++++++++++++++++-------
> kernel/bpf/trampoline.c | 18 ++++++++++++------
> net/bpf/bpf_dummy_struct_ops.c | 4 +++-
> 6 files changed, 50 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index e1390d1e331b..128c8ec9164e 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -2780,12 +2780,14 @@ void arch_free_bpf_trampoline(void *image, unsigned int size)
> bpf_prog_pack_free(image, size);
> }
>
> -void arch_protect_bpf_trampoline(void *image, unsigned int size)
> +int arch_protect_bpf_trampoline(void *image, unsigned int size)
> {
> + return 0;
> }
>
> -void arch_unprotect_bpf_trampoline(void *image, unsigned int size)
> +int arch_unprotect_bpf_trampoline(void *image, unsigned int size)
> {
> + return 0;
> }
>
> int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image_end,
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index b86bd15a051d..bb2723c264df 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1116,8 +1116,8 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> void *func_addr);
> void *arch_alloc_bpf_trampoline(unsigned int size);
> void arch_free_bpf_trampoline(void *image, unsigned int size);
> -void arch_protect_bpf_trampoline(void *image, unsigned int size);
> -void arch_unprotect_bpf_trampoline(void *image, unsigned int size);
> +int __must_check arch_protect_bpf_trampoline(void *image, unsigned int size);
> +int arch_unprotect_bpf_trampoline(void *image, unsigned int size);
> int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
> struct bpf_tramp_links *tlinks, void *func_addr);
>
> diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
> index 0decd862dfe0..d920afb0dd60 100644
> --- a/kernel/bpf/bpf_struct_ops.c
> +++ b/kernel/bpf/bpf_struct_ops.c
> @@ -488,7 +488,9 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
> if (err)
> goto reset_unlock;
> }
> - arch_protect_bpf_trampoline(st_map->image, PAGE_SIZE);
> + err = arch_protect_bpf_trampoline(st_map->image, PAGE_SIZE);
> + if (err)
> + goto reset_unlock;
> /* Let bpf_link handle registration & unregistration.
> *
> * Pair with smp_load_acquire() during lookup_elem().
> @@ -497,7 +499,10 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
> goto unlock;
> }
>
> - arch_protect_bpf_trampoline(st_map->image, PAGE_SIZE);
> + err = arch_protect_bpf_trampoline(st_map->image, PAGE_SIZE);
> + if (err)
> + goto reset_unlock;
> +
> err = st_ops->reg(kdata);
> if (likely(!err)) {
> /* This refcnt increment on the map here after
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index c49619ef55d0..eb2256ba6daf 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -898,23 +898,31 @@ static LIST_HEAD(pack_list);
> static struct bpf_prog_pack *alloc_new_pack(bpf_jit_fill_hole_t bpf_fill_ill_insns)
> {
> struct bpf_prog_pack *pack;
> + int err;
>
> pack = kzalloc(struct_size(pack, bitmap, BITS_TO_LONGS(BPF_PROG_CHUNK_COUNT)),
> GFP_KERNEL);
> if (!pack)
> return NULL;
> pack->ptr = bpf_jit_alloc_exec(BPF_PROG_PACK_SIZE);
> - if (!pack->ptr) {
> - kfree(pack);
> - return NULL;
> - }
> + if (!pack->ptr)
> + goto out;
> bpf_fill_ill_insns(pack->ptr, BPF_PROG_PACK_SIZE);
> bitmap_zero(pack->bitmap, BPF_PROG_PACK_SIZE / BPF_PROG_CHUNK_SIZE);
> - list_add_tail(&pack->list, &pack_list);
>
> set_vm_flush_reset_perms(pack->ptr);
> - set_memory_rox((unsigned long)pack->ptr, BPF_PROG_PACK_SIZE / PAGE_SIZE);
> + err = set_memory_rox((unsigned long)pack->ptr,
> + BPF_PROG_PACK_SIZE / PAGE_SIZE);
> + if (err)
> + goto out_free;
> + list_add_tail(&pack->list, &pack_list);
> return pack;
> +
> +out_free:
> + bpf_jit_free_exec(pack->ptr);
> +out:
> + kfree(pack);
> + return NULL;
> }
>
> void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns)
> @@ -929,9 +937,16 @@ void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns)
> size = round_up(size, PAGE_SIZE);
> ptr = bpf_jit_alloc_exec(size);
> if (ptr) {
> + int err;
> +
> bpf_fill_ill_insns(ptr, size);
> set_vm_flush_reset_perms(ptr);
> - set_memory_rox((unsigned long)ptr, size / PAGE_SIZE);
> + err = set_memory_rox((unsigned long)ptr,
> + size / PAGE_SIZE);
> + if (err) {
> + bpf_jit_free_exec(ptr);
> + ptr = NULL;
> + }
> }
> goto out;
> }
> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> index d382f5ebe06c..6e64ac9083b6 100644
> --- a/kernel/bpf/trampoline.c
> +++ b/kernel/bpf/trampoline.c
> @@ -456,7 +456,9 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut
> if (err < 0)
> goto out_free;
>
> - arch_protect_bpf_trampoline(im->image, im->size);
> + err = arch_protect_bpf_trampoline(im->image, im->size);
> + if (err)
> + goto out_free;
>
> WARN_ON(tr->cur_image && total == 0);
> if (tr->cur_image)
> @@ -1072,17 +1074,21 @@ void __weak arch_free_bpf_trampoline(void *image, unsigned int size)
> bpf_jit_free_exec(image);
> }
>
> -void __weak arch_protect_bpf_trampoline(void *image, unsigned int size)
> +int __weak arch_protect_bpf_trampoline(void *image, unsigned int size)
nit: Should we add __must_check as well here?
> {
> WARN_ON_ONCE(size > PAGE_SIZE);
> - set_memory_rox((long)image, 1);
> + return set_memory_rox((long)image, 1);
> }
>
> -void __weak arch_unprotect_bpf_trampoline(void *image, unsigned int size)
> +int __weak arch_unprotect_bpf_trampoline(void *image, unsigned int size)
> {
> + int err;
> WARN_ON_ONCE(size > PAGE_SIZE);
> - set_memory_nx((long)image, 1);
> - set_memory_rw((long)image, 1);
> +
> + err = set_memory_nx((long)image, 1);
> + if (err)
> + return err;
> + return set_memory_rw((long)image, 1);
> }
Do we still need this? It looks like this does not have an in-tree user anymore.
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index c5b461dda438..132c8ffba109 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -2180,10 +2180,6 @@ void arch_protect_bpf_trampoline(void *image, unsigned int size)
{
}
-void arch_unprotect_bpf_trampoline(void *image, unsigned int size)
-{
-}
-
int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *ro_image,
void *ro_image_end, const struct btf_func_model *m,
u32 flags, struct bpf_tramp_links *tlinks,
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index a7ba8e178645..7a56d2d84512 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -3008,10 +3008,6 @@ void arch_protect_bpf_trampoline(void *image, unsigned int size)
{
}
-void arch_unprotect_bpf_trampoline(void *image, unsigned int size)
-{
-}
-
int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image_end,
const struct btf_func_model *m, u32 flags,
struct bpf_tramp_links *tlinks,
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4f20f62f9d63..d89bdefb42e2 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1117,7 +1117,6 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
void *arch_alloc_bpf_trampoline(unsigned int size);
void arch_free_bpf_trampoline(void *image, unsigned int size);
void arch_protect_bpf_trampoline(void *image, unsigned int size);
-void arch_unprotect_bpf_trampoline(void *image, unsigned int size);
int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
struct bpf_tramp_links *tlinks, void *func_addr);
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index db7599c59c78..04fd1abd3661 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -1078,13 +1078,6 @@ void __weak arch_protect_bpf_trampoline(void *image, unsigned int size)
set_memory_rox((long)image, 1);
}
-void __weak arch_unprotect_bpf_trampoline(void *image, unsigned int size)
-{
- WARN_ON_ONCE(size > PAGE_SIZE);
- set_memory_nx((long)image, 1);
- set_memory_rw((long)image, 1);
-}
-
int __weak arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
struct bpf_tramp_links *tlinks, void *func_addr)
{
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