diff mbox series

[bpf-next,2/2] bpf: Enforce W^X for bpf trampoline

Message ID 20220923211837.3044723-3-song@kernel.org (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series enforce W^X for trampoline and dispatcher | expand

Checks

Context Check Description
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netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1362 this patch: 1362
netdev/cc_maintainers warning 6 maintainers not CCed: sdf@google.com andrii@kernel.org yhs@fb.com jolsa@kernel.org kpsingh@kernel.org martin.lau@linux.dev
netdev/build_clang success Errors and warnings before: 159 this patch: 159
netdev/module_param success Was 0 now: 0
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netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1354 this patch: 1354
netdev/checkpatch warning CHECK: multiple assignments should be avoided
netdev/kdoc success Errors and warnings before: 0 this patch: 0
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Commit Message

Song Liu Sept. 23, 2022, 9:18 p.m. UTC 
Mark the trampoline as RO+X after arch_prepare_bpf_trampoline, so that
the trampoine follows W^X rule strictly. This will turn off warnings like

CPA refuse W^X violation: 8000000000000163 -> 0000000000000163 range: ...

Also remove bpf_jit_alloc_exec_page(), since it is not used any more.

Signed-off-by: Song Liu <song@kernel.org>
---
 include/linux/bpf.h     |  1 -
 kernel/bpf/trampoline.c | 22 +++++-----------------
 2 files changed, 5 insertions(+), 18 deletions(-)
diff mbox series

Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a8d0cfe14372..44a3d6b3c924 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1008,7 +1008,6 @@  int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs);
 void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from,
 				struct bpf_prog *to);
 /* Called only from JIT-enabled code, so there's no need for stubs. */
-void *bpf_jit_alloc_exec_page(void);
 void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym);
 void bpf_image_ksym_del(struct bpf_ksym *ksym);
 void bpf_ksym_add(struct bpf_ksym *ksym);
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 41b67eb83ab3..6f7b939321d6 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -116,22 +116,6 @@  bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
 		(ptype == BPF_PROG_TYPE_LSM && eatype == BPF_LSM_MAC);
 }
 
-void *bpf_jit_alloc_exec_page(void)
-{
-	void *image;
-
-	image = bpf_jit_alloc_exec(PAGE_SIZE);
-	if (!image)
-		return NULL;
-
-	set_vm_flush_reset_perms(image);
-	/* Keep image as writeable. The alternative is to keep flipping ro/rw
-	 * every time new program is attached or detached.
-	 */
-	set_memory_x((long)image, 1);
-	return image;
-}
-
 void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym)
 {
 	ksym->start = (unsigned long) data;
@@ -404,9 +388,10 @@  static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
 		goto out_free_im;
 
 	err = -ENOMEM;
-	im->image = image = bpf_jit_alloc_exec_page();
+	im->image = image = bpf_jit_alloc_exec(PAGE_SIZE);
 	if (!image)
 		goto out_uncharge;
+	set_vm_flush_reset_perms(image);
 
 	err = percpu_ref_init(&im->pcref, __bpf_tramp_image_release, 0, GFP_KERNEL);
 	if (err)
@@ -483,6 +468,9 @@  static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut
 	if (err < 0)
 		goto out;
 
+	set_memory_ro((long)im->image, 1);
+	set_memory_x((long)im->image, 1);
+
 	WARN_ON(tr->cur_image && tr->selector == 0);
 	WARN_ON(!tr->cur_image && tr->selector);
 	if (tr->cur_image)