+ alloc_tag-fix-set_codetag_empty-when-config_mem_alloc_profiling_debug.patch added to mm-hotfixes-unstable branch

+ alloc_tag-fix-set_codetag_empty-when-config_mem_alloc_profiling_debug.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: alloc_tag: fix set_codetag_empty() when !CONFIG_MEM_ALLOC_PROFILING_DEBUG
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     alloc_tag-fix-set_codetag_empty-when-config_mem_alloc_profiling_debug.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/alloc_tag-fix-set_codetag_empty-when-config_mem_alloc_profiling_debug.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Suren Baghdasaryan <surenb@google.com>
Subject: alloc_tag: fix set_codetag_empty() when !CONFIG_MEM_ALLOC_PROFILING_DEBUG
Date: Fri, 29 Nov 2024 16:14:23 -0800

It was recently noticed that set_codetag_empty() might be used not only to
mark NULL alloctag references as empty to avoid warnings but also to reset
valid tags (in clear_page_tag_ref()).  Since set_codetag_empty() is
defined as NOOP for CONFIG_MEM_ALLOC_PROFILING_DEBUG=n, such use of
set_codetag_empty() leads to subtle bugs.  Fix set_codetag_empty() for
CONFIG_MEM_ALLOC_PROFILING_DEBUG=n to reset the tag reference.

Link: https://lkml.kernel.org/r/20241130001423.1114965-2-surenb@google.com
Fixes: a8fc28dad6d5 ("alloc_tag: introduce clear_page_tag_ref() helper function")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reported-by: David Wang <00107082@163.com>
Closes: https://lore.kernel.org/lkml/20241124074318.399027-1-00107082@163.com/
Cc: David Wang <00107082@163.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/alloc_tag.h |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/include/linux/alloc_tag.h~alloc_tag-fix-set_codetag_empty-when-config_mem_alloc_profiling_debug
+++ a/include/linux/alloc_tag.h
@@ -63,7 +63,12 @@ static inline void set_codetag_empty(uni
 #else /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */
 
 static inline bool is_codetag_empty(union codetag_ref *ref) { return false; }
-static inline void set_codetag_empty(union codetag_ref *ref) {}
+
+static inline void set_codetag_empty(union codetag_ref *ref)
+{
+	if (ref)
+		ref->ct = NULL;
+}
 
 #endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */
 
_

Patches currently in -mm which might be from surenb@google.com are

alloc_tag-fix-module-allocation-tags-populated-area-calculation.patch
alloc_tag-fix-set_codetag_empty-when-config_mem_alloc_profiling_debug.patch
mm-convert-mm_lock_seq-to-a-proper-seqcount.patch
mm-introduce-mmap_lock_speculation_beginend.patch