Merge branch 'refactor-lock-management'

Kumar Kartikeya Dwivedi says:

====================
Refactor lock management

This set refactors lock management in the verifier in preparation for
spin locks that can be acquired multiple times. In addition to this,
unnecessary code special case reference leak logic for callbacks is also
dropped, that is no longer necessary. See patches for details.

Changelog:
----------
v5 -> v6
v5: https://lore.kernel.org/bpf/20241109225243.2306756-1-memxor@gmail.com

 * Move active_locks mutation to {acquire,release}_lock_state (Alexei)

v4 -> v5
v4: https://lore.kernel.org/bpf/20241109074347.1434011-1-memxor@gmail.com

 * Make active_locks part of bpf_func_state (Alexei)
 * Remove unneeded in_callback_fn logic for references

v3 -> v4
v3: https://lore.kernel.org/bpf/20241104151716.2079893-1-memxor@gmail.com

* Address comments from Alexei
  * Drop struct bpf_active_lock definition
  * Name enum type, expand definition to multiple lines
  * s/REF_TYPE_BPF_LOCK/REF_TYPE_LOCK/g
  * Change active_lock type to int
  * Fix type of 'type' in acquire_lock_state
  * Filter by taking type explicitly in find_lock_state
  * WARN for default case in refsafe switch statement

v2 -> v3
v2: https://lore.kernel.org/bpf/20241103212252.547071-1-memxor@gmail.com

  * Rebase on bpf-next to resolve merge conflict

v1 -> v2
v1: https://lore.kernel.org/bpf/20241103205856.345580-1-memxor@gmail.com

  * Fix refsafe state comparison to check callback_ref and ptr separately.
====================

Link: https://lore.kernel.org/r/20241109231430.2475236-1-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

1 files changed, 12 insertions, 28 deletions

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 4513372c5bc8..3a74033d49c4 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -48,22 +48,6 @@ enum bpf_reg_liveness {
 	REG_LIVE_DONE = 0x8, /* liveness won't be updating this register anymore */
 };
 
-/* For every reg representing a map value or allocated object pointer,
- * we consider the tuple of (ptr, id) for them to be unique in verifier
- * context and conside them to not alias each other for the purposes of
- * tracking lock state.
- */
-struct bpf_active_lock {
-	/* This can either be reg->map_ptr or reg->btf. If ptr is NULL,
-	 * there's no active lock held, and other fields have no
-	 * meaning. If non-NULL, it indicates that a lock is held and
-	 * id member has the reg->id of the register which can be >= 0.
-	 */
-	void *ptr;
-	/* This will be reg->id */
-	u32 id;
-};
-
 #define ITER_PREFIX "bpf_iter_"
 
 enum bpf_iter_state {
@@ -266,6 +250,13 @@ struct bpf_stack_state {
 };
 
 struct bpf_reference_state {
+	/* Each reference object has a type. Ensure REF_TYPE_PTR is zero to
+	 * default to pointer reference on zero initialization of a state.
+	 */
+	enum ref_state_type {
+		REF_TYPE_PTR = 0,
+		REF_TYPE_LOCK,
+	} type;
 	/* Track each reference created with a unique id, even if the same
 	 * instruction creates the reference multiple times (eg, via CALL).
 	 */
@@ -274,17 +265,10 @@ struct bpf_reference_state {
 	 * is used purely to inform the user of a reference leak.
 	 */
 	int insn_idx;
-	/* There can be a case like:
-	 * main (frame 0)
-	 *  cb (frame 1)
-	 *   func (frame 3)
-	 *    cb (frame 4)
-	 * Hence for frame 4, if callback_ref just stored boolean, it would be
-	 * impossible to distinguish nested callback refs. Hence store the
-	 * frameno and compare that to callback_ref in check_reference_leak when
-	 * exiting a callback function.
-	 */
-	int callback_ref;
+	/* Use to keep track of the source object of a lock, to ensure
+	 * it matches on unlock.
+	 */
+	void *ptr;
 };
 
 struct bpf_retval_range {
@@ -332,6 +316,7 @@ struct bpf_func_state {
 
 	/* The following fields should be last. See copy_func_state() */
 	int acquired_refs;
+	int active_locks;
 	struct bpf_reference_state *refs;
 	/* The state of the stack. Each element of the array describes BPF_REG_SIZE
 	 * (i.e. 8) bytes worth of stack memory.
@@ -434,7 +419,6 @@ struct bpf_verifier_state {
 	u32 insn_idx;
 	u32 curframe;
 
-	struct bpf_active_lock active_lock;
 	bool speculative;
 	bool active_rcu_lock;
 	u32 active_preempt_lock;