Merge branch 'bpf-verifier-retval-logic-fixes'

Andrii Nakryiko says:

====================
BPF verifier retval logic fixes

This patch set fixes BPF verifier logic around validating and enforcing return
values for BPF programs that have specific range of expected return values.
Both sync and async callbacks have similar logic and are fixes as well.
A few tests are added that would fail without the fixes in this patch set.

Also, while at it, we update retval checking logic to use smin/smax range
instead of tnum, avoiding future potential issues if expected range cannot be
represented precisely by tnum (e.g., [0, 2] is not representable by tnum and
is treated as [0, 3]).

There is a little bit of refactoring to unify async callback and program exit
logic to avoid duplication of checks as much as possible.

v4->v5:
  - fix timer_bad_ret test on no-alu32 flavor (CI);
v3->v4:
  - add back bpf_func_state rearrangement patch;
  - simplified patch #4 as suggested (Shung-Hsi);
v2->v3:
  - more carefullly switch from umin/umax to smin/smax;
v1->v2:
  - drop tnum from retval checks (Eduard);
  - use smin/smax instead of umin/umax (Alexei).
====================

Link: https://lore.kernel.org/r/20231202175705.885270-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index d99a636d36a7..3378cc753061 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -275,6 +275,11 @@ struct bpf_reference_state {
 	int callback_ref;
 };
 
+struct bpf_retval_range {
+	s32 minval;
+	s32 maxval;
+};
+
 /* state of the program:
  * type of all registers and stack info
  */
@@ -297,8 +302,8 @@ struct bpf_func_state {
 	 * void foo(void) { bpf_timer_set_callback(,foo); }
 	 */
 	u32 async_entry_cnt;
+	struct bpf_retval_range callback_ret_range;
 	bool in_callback_fn;
-	struct tnum callback_ret_range;
 	bool in_async_callback_fn;
 	bool in_exception_callback_fn;
 	/* For callback calling functions that limit number of possible
@@ -316,8 +321,8 @@ struct bpf_func_state {
 	/* The following fields should be last. See copy_func_state() */
 	int acquired_refs;
 	struct bpf_reference_state *refs;
-	int allocated_stack;
 	struct bpf_stack_state *stack;
+	int allocated_stack;
 };
 
 struct bpf_idx_pair {