Re: [PATCH bpf-next v3 2/2] bpf: Check return from set_memory_rox()
From: Kui-Feng Lee
Date: Fri Mar 15 2024 - 14:11:34 EST
On 3/15/24 10:06, 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_rox() function and add
__must_check flag to arch_protect_bpf_trampoline().
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
v3:
- Rebased and handled conflict in kernel/bpf/bpf_struct_ops.c
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/arm64/net/bpf_jit_comp.c | 3 ++-
arch/x86/net/bpf_jit_comp.c | 3 ++-
include/linux/bpf.h | 2 +-
kernel/bpf/bpf_struct_ops.c | 7 +++++--
kernel/bpf/core.c | 29 ++++++++++++++++++++++-------
kernel/bpf/trampoline.c | 8 +++++---
net/bpf/bpf_dummy_struct_ops.c | 4 +++-
7 files changed, 40 insertions(+), 16 deletions(-)
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 132c8ffba109..bc16eb694657 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -2176,8 +2176,9 @@ 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;
}
int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *ro_image,
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 7a56d2d84512..4900b1ee019f 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -3004,8 +3004,9 @@ 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;
}
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 d89bdefb42e2..17843e66a1d3 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1116,7 +1116,7 @@ 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);
+int __must_check arch_protect_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 43356faaa057..ca1d9b87c475 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -742,8 +742,11 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
if (err)
goto reset_unlock;
}
- for (i = 0; i < st_map->image_pages_cnt; i++)
- arch_protect_bpf_trampoline(st_map->image_pages[i], PAGE_SIZE);
+ for (i = 0; i < st_map->image_pages_cnt && !err; i++)
+ err = arch_protect_bpf_trampoline(st_map->image_pages[i], PAGE_SIZE);
+
+ if (err)
nit: Can it be more specific? I mean to check err < 0, so we can reason
that this function never returns a positive value other than 0.
+ goto reset_unlock;
if (st_map->map.map_flags & BPF_F_LINK) {
err = 0;
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 63f100def31b..1e761c3c66db 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -908,23 +908,31 @@ 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)
@@ -939,9 +947,16 @@ 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 04fd1abd3661..cc50607f8d8c 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;
Same here
- 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)
@@ -1072,10 +1074,10 @@ 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)
{
WARN_ON_ONCE(size > PAGE_SIZE);
- set_memory_rox((long)image, 1);
+ return set_memory_rox((long)image, 1);
}
int __weak arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
diff --git a/net/bpf/bpf_dummy_struct_ops.c b/net/bpf/bpf_dummy_struct_ops.c
index de33dc1b0daa..25b75844891a 100644
--- a/net/bpf/bpf_dummy_struct_ops.c
+++ b/net/bpf/bpf_dummy_struct_ops.c
@@ -133,7 +133,9 @@ int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
if (err < 0)
goto out;
- arch_protect_bpf_trampoline(image, PAGE_SIZE);
+ err = arch_protect_bpf_trampoline(image, PAGE_SIZE);
+ if (err)
Same here.
+ goto out;
prog_ret = dummy_ops_call_op(image, args);
err = dummy_ops_copy_args(args);