codetag: debug: skip objext checking when it's for objext itself

objext objects are created with __GFP_NO_OBJ_EXT flag and therefore have
no corresponding objext themselves (otherwise we would get an infinite
recursion). When freeing these objects their codetag will be empty and
when CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled this will lead to false
warnings. Introduce CODETAG_EMPTY special codetag value to mark
allocations which intentionally lack codetag to avoid these warnings.
Set objext codetags to CODETAG_EMPTY before freeing to indicate that
the codetag is expected to be empty.

Link: https://lkml.kernel.org/r/20240321163705.3067592-34-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Tested-by: Kees Cook <keescook@chromium.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andreas Hindborg <a.hindborg@samsung.com>
Cc: Benno Lossin <benno.lossin@proton.me>
Cc: "Björn Roy Baron" <bjorn3_gh@protonmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Gary Guo <gary@garyguo.net>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
index d18388c0e9e1..3af5d6a5ced4 100644
--- a/include/linux/alloc_tag.h
+++ b/include/linux/alloc_tag.h
@@ -29,6 +29,27 @@ struct alloc_tag {
 	struct alloc_tag_counters __percpu	*counters;
 } __aligned(8);
 
+#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
+
+#define CODETAG_EMPTY	((void *)1)
+
+static inline bool is_codetag_empty(union codetag_ref *ref)
+{
+	return ref->ct == CODETAG_EMPTY;
+}
+
+static inline void set_codetag_empty(union codetag_ref *ref)
+{
+	if (ref)
+		ref->ct = CODETAG_EMPTY;
+}
+
+#else /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */
+
+static inline bool is_codetag_empty(union codetag_ref *ref) { return false; }
+
+#endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */
+
 #ifdef CONFIG_MEM_ALLOC_PROFILING
 
 struct codetag_bytes {
@@ -151,6 +172,11 @@ static inline void alloc_tag_sub(union codetag_ref *ref, size_t bytes)
 	if (!ref || !ref->ct)
 		return;
 
+	if (is_codetag_empty(ref)) {
+		ref->ct = NULL;
+		return;
+	}
+
 	tag = ct_to_alloc_tag(ref->ct);
 
 	this_cpu_sub(tag->counters->bytes, bytes);