[PATCH bpf-next 2/3] bpf: Keep im address consistent between dry run and real patching
Pu Lehui
pulehui at huaweicloud.com
Tue Jan 23 02:32:40 PST 2024
From: Pu Lehui <pulehui at huawei.com>
In __arch_prepare_bpf_trampoline, we emit instructions to store the
address of im to register and then pass it to __bpf_tramp_enter and
__bpf_tramp_exit functions. Currently we use fake im in
arch_bpf_trampoline_size for the dry run, and then allocate new im for
the real patching. This is fine for architectures that use fixed
instructions to generate addresses. However, for architectures that use
dynamic instructions to generate addresses, this may make the front and
rear images inconsistent, leading to patching overflow. We can extract
the im allocation ahead of the dry run and pass the allocated im to
arch_bpf_trampoline_size, so that we can ensure that im is consistent in
dry run and real patching.
Signed-off-by: Pu Lehui <pulehui at huawei.com>
---
arch/arm64/net/bpf_jit_comp.c | 7 +++---
arch/riscv/net/bpf_jit_comp64.c | 7 +++---
arch/s390/net/bpf_jit_comp.c | 7 +++---
arch/x86/net/bpf_jit_comp.c | 7 +++---
include/linux/bpf.h | 4 +--
kernel/bpf/bpf_struct_ops.c | 2 +-
kernel/bpf/trampoline.c | 43 ++++++++++++++++-----------------
7 files changed, 36 insertions(+), 41 deletions(-)
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 8955da5c47cf..fad760f14a96 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -2041,14 +2041,13 @@ static int btf_func_model_nregs(const struct btf_func_model *m)
return nregs;
}
-int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
- struct bpf_tramp_links *tlinks, void *func_addr)
+int arch_bpf_trampoline_size(struct bpf_tramp_image *im, const struct btf_func_model *m,
+ u32 flags, struct bpf_tramp_links *tlinks, void *func_addr)
{
struct jit_ctx ctx = {
.image = NULL,
.idx = 0,
};
- struct bpf_tramp_image im;
int nregs, ret;
nregs = btf_func_model_nregs(m);
@@ -2056,7 +2055,7 @@ int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
if (nregs > 8)
return -ENOTSUPP;
- ret = prepare_trampoline(&ctx, &im, tlinks, func_addr, nregs, flags);
+ ret = prepare_trampoline(&ctx, im, tlinks, func_addr, nregs, flags);
if (ret < 0)
return ret;
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 719a97e7edb2..5c4e0ac389d0 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -1030,17 +1030,16 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
return ret;
}
-int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
- struct bpf_tramp_links *tlinks, void *func_addr)
+int arch_bpf_trampoline_size(struct bpf_tramp_image *im, const struct btf_func_model *m,
+ u32 flags, struct bpf_tramp_links *tlinks, void *func_addr)
{
- struct bpf_tramp_image im;
struct rv_jit_context ctx;
int ret;
ctx.ninsns = 0;
ctx.insns = NULL;
ctx.ro_insns = NULL;
- ret = __arch_prepare_bpf_trampoline(&im, m, tlinks, func_addr, flags, &ctx);
+ ret = __arch_prepare_bpf_trampoline(im, m, tlinks, func_addr, flags, &ctx);
return ret < 0 ? ret : ninsns_rvoff(ctx.ninsns);
}
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index b418333bb086..adf289eee6cd 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -2638,16 +2638,15 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
return 0;
}
-int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
- struct bpf_tramp_links *tlinks, void *orig_call)
+int arch_bpf_trampoline_size(struct bpf_tramp_image *im, const struct btf_func_model *m,
+ u32 flags, struct bpf_tramp_links *tlinks, void *orig_call)
{
- struct bpf_tramp_image im;
struct bpf_tramp_jit tjit;
int ret;
memset(&tjit, 0, sizeof(tjit));
- ret = __arch_prepare_bpf_trampoline(&im, &tjit, m, flags,
+ ret = __arch_prepare_bpf_trampoline(im, &tjit, m, flags,
tlinks, orig_call);
return ret < 0 ? ret : tjit.common.prg;
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index e1390d1e331b..fdef44913643 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -2817,10 +2817,9 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
return ret;
}
-int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
- struct bpf_tramp_links *tlinks, void *func_addr)
+int arch_bpf_trampoline_size(struct bpf_tramp_image *im, const struct btf_func_model *m,
+ u32 flags, struct bpf_tramp_links *tlinks, void *func_addr)
{
- struct bpf_tramp_image im;
void *image;
int ret;
@@ -2835,7 +2834,7 @@ int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
if (!image)
return -ENOMEM;
- ret = __arch_prepare_bpf_trampoline(&im, image, image + PAGE_SIZE, image,
+ ret = __arch_prepare_bpf_trampoline(im, image, image + PAGE_SIZE, image,
m, flags, tlinks, func_addr);
bpf_jit_free_exec(image);
return ret;
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 377857b232c6..d3a486e12b17 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1114,8 +1114,8 @@ 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);
+int arch_bpf_trampoline_size(struct bpf_tramp_image *im, const struct btf_func_model *m,
+ u32 flags, struct bpf_tramp_links *tlinks, void *func_addr);
u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
struct bpf_tramp_run_ctx *run_ctx);
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index e2e1bf3c69a3..8b3c6cc7ea94 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -363,7 +363,7 @@ int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
if (model->ret_size > 0)
flags |= BPF_TRAMP_F_RET_FENTRY_RET;
- size = arch_bpf_trampoline_size(model, flags, tlinks, NULL);
+ size = arch_bpf_trampoline_size(NULL, model, flags, tlinks, NULL);
if (size < 0)
return size;
if (size > (unsigned long)image_end - (unsigned long)image)
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index d382f5ebe06c..25621d97f3ca 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -349,20 +349,15 @@ static void bpf_tramp_image_put(struct bpf_tramp_image *im)
call_rcu_tasks_trace(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
}
-static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, int size)
+static int bpf_tramp_image_alloc(struct bpf_tramp_image *im, u64 key, int size)
{
- struct bpf_tramp_image *im;
struct bpf_ksym *ksym;
void *image;
- int err = -ENOMEM;
-
- im = kzalloc(sizeof(*im), GFP_KERNEL);
- if (!im)
- goto out;
+ int err;
err = bpf_jit_charge_modmem(size);
if (err)
- goto out_free_im;
+ goto out;
im->size = size;
err = -ENOMEM;
@@ -378,16 +373,14 @@ static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, int size)
INIT_LIST_HEAD_RCU(&ksym->lnode);
snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu", key);
bpf_image_ksym_add(image, size, ksym);
- return im;
+ return 0;
out_free_image:
arch_free_bpf_trampoline(im->image, im->size);
out_uncharge:
bpf_jit_uncharge_modmem(size);
-out_free_im:
- kfree(im);
out:
- return ERR_PTR(err);
+ return err;
}
static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex)
@@ -432,23 +425,27 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut
tr->flags |= BPF_TRAMP_F_ORIG_STACK;
#endif
- size = arch_bpf_trampoline_size(&tr->func.model, tr->flags,
+ im = kzalloc(sizeof(*im), GFP_KERNEL);
+ if (!im) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ size = arch_bpf_trampoline_size(im, &tr->func.model, tr->flags,
tlinks, tr->func.addr);
if (size < 0) {
err = size;
- goto out;
+ goto out_free_im;
}
if (size > PAGE_SIZE) {
err = -E2BIG;
- goto out;
+ goto out_free_im;
}
- im = bpf_tramp_image_alloc(tr->key, size);
- if (IS_ERR(im)) {
- err = PTR_ERR(im);
- goto out;
- }
+ err = bpf_tramp_image_alloc(im, tr->key, size);
+ if (err < 0)
+ goto out_free_im;
err = arch_prepare_bpf_trampoline(im, im->image, im->image + size,
&tr->func.model, tr->flags, tlinks,
@@ -496,6 +493,8 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut
out_free:
bpf_tramp_image_free(im);
+out_free_im:
+ kfree_rcu(im, rcu);
goto out;
}
@@ -1085,8 +1084,8 @@ void __weak arch_unprotect_bpf_trampoline(void *image, unsigned int size)
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)
+int __weak arch_bpf_trampoline_size(struct bpf_tramp_image *im, const struct btf_func_model *m,
+ u32 flags, struct bpf_tramp_links *tlinks, void *func_addr)
{
return -ENOTSUPP;
}
--
2.34.1
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