[PATCH v3 17/20] bpf: Use vmalloc special flag

[Rick Edgecombe]

Use new flag VM_FLUSH_RESET_PERMS for handling freeing of special
permissioned memory in vmalloc and remove places where memory was set RW
before freeing which is no longer needed. Don't track if the memory is RO
anymore because it is now tracked in vmalloc.

Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
---
 include/linux/filter.h | 17 +++--------------
 kernel/bpf/core.c      |  1 -
 2 files changed, 3 insertions(+), 15 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index b9f93e62db96..f7b6c8a2e591 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -20,6 +20,7 @@
 #include <linux/set_memory.h>
 #include <linux/kallsyms.h>
 #include <linux/if_vlan.h>
+#include <linux/vmalloc.h>
 
 #include <net/sch_generic.h>
 
@@ -483,7 +484,6 @@ struct bpf_prog {
 	u16			pages;		/* Number of allocated pages */
 	u16			jited:1,	/* Is our filter JIT'ed? */
 				jit_requested:1,/* archs need to JIT the prog */
-				undo_set_mem:1,	/* Passed set_memory_ro() checkpoint */
 				gpl_compatible:1, /* Is filter GPL compatible? */
 				cb_access:1,	/* Is control block accessed? */
 				dst_needed:1,	/* Do we need dst entry? */
@@ -681,27 +681,17 @@ bpf_ctx_narrow_access_ok(u32 off, u32 size, u32 size_default)
 
 static inline void bpf_prog_lock_ro(struct bpf_prog *fp)
 {
-	fp->undo_set_mem = 1;
+	set_vm_flush_reset_perms(fp);
 	set_memory_ro((unsigned long)fp, fp->pages);
 }
 
-static inline void bpf_prog_unlock_ro(struct bpf_prog *fp)
-{
-	if (fp->undo_set_mem)
-		set_memory_rw((unsigned long)fp, fp->pages);
-}
-
 static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
 {
+	set_vm_flush_reset_perms(hdr);
 	set_memory_ro((unsigned long)hdr, hdr->pages);
 	set_memory_x((unsigned long)hdr, hdr->pages);
 }
 
-static inline void bpf_jit_binary_unlock_ro(struct bpf_binary_header *hdr)
-{
-	set_memory_rw((unsigned long)hdr, hdr->pages);
-}
-
 static inline struct bpf_binary_header *
 bpf_jit_binary_hdr(const struct bpf_prog *fp)
 {
@@ -736,7 +726,6 @@ void __bpf_prog_free(struct bpf_prog *fp);
 
 static inline void bpf_prog_unlock_free(struct bpf_prog *fp)
 {
-	bpf_prog_unlock_ro(fp);
 	__bpf_prog_free(fp);
 }
 
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 19c49313c709..465c1c3623e8 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -804,7 +804,6 @@ void __weak bpf_jit_free(struct bpf_prog *fp)
 	if (fp->jited) {
 		struct bpf_binary_header *hdr = bpf_jit_binary_hdr(fp);
 
-		bpf_jit_binary_unlock_ro(hdr);
 		bpf_jit_binary_free(hdr);
 
 		WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(fp));
-- 
2.17.1