From c6e5c0b9a493891634d0a413c3485930a28a8903 Mon Sep 17 00:00:00 2001 From: Hao Ge Date: Wed, 16 Sep 2026 15:55:57 +0800 Subject: [PATCH] mm/alloc_tag: account for reserved tag ids in the kernel tag check The tag ids stored in the page flags include two reserved markers. Id 0 means the page has no tag and id 1 means the tag was cleared, so real tags start at CODETAG_ID_FIRST. The kernel-side check in alloc_tag_sec_init() compared kernel_tags.count alone against the addressable limit, so with the count at or just under the limit the last tag ids wrapped into those markers. Pages allocated through them then look the same as untagged pages on free, nothing is ever subtracted from the real tag and /proc/allocinfo shows that memory as still allocated. Add the missing CODETAG_ID_FIRST, same as tags_addressable(). Link: https://lore.kernel.org/20260916075557.121316-1-hao.ge@linux.dev Fixes: 4835f747d3ed ("alloc_tag: support for page allocation tag compression") Signed-off-by: Hao Ge Signed-off-by: Andrew Morton Acked-by: Suren Baghdasaryan Cc: --- mm/alloc_tag.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c index b33410310477..82e2c3448dcf 100644 --- a/mm/alloc_tag.c +++ b/mm/alloc_tag.c @@ -621,7 +621,7 @@ void __init alloc_tag_sec_init(void) kernel_tags.count = last_codetag - kernel_tags.first_tag; /* Check if kernel tags fit into page flags */ - if (kernel_tags.count > (1UL << NR_UNUSED_PAGEFLAG_BITS)) { + if (CODETAG_ID_FIRST + kernel_tags.count > (1UL << NR_UNUSED_PAGEFLAG_BITS)) { shutdown_mem_profiling(false); /* allocinfo file does not exist yet */ pr_err("%lu allocation tags cannot be references using %d available page flag bits. Memory allocation profiling is disabled!\n", kernel_tags.count, NR_UNUSED_PAGEFLAG_BITS);