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b=lebhn8hKMRA0/WLMRMGCHsbQDXYJUTUh6x4EEOCp8ZbdPu5C+3wGbUZs3aqSwK6aR QNOIh+f7uT2EPwzP7ZZxXzGMaICmg8NPBF+SAHItFMZsvePpfigP6015XfzemRck2a MxDT9cAkA8TeqydlMsV0Gc4kBNStS12VQ311adG0= Date: Tue, 11 Aug 2026 18:29:14 -0700 From: Andrew Morton To: Hui Su Cc: ryabinin.a.a@gmail.com, glider@google.com, andreyknvl@gmail.com, dvyukov@google.com, vincenzo.frascino@arm.com, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sashiko Subject: Re: [PATCH] kasan: fix quarantine_size accounting during cache removal Message-Id: <20260811182914.ed2cba4ef1a8a88335b9edab@linux-foundation.org> In-Reply-To: <20260811073332.1351893-1-sh_def@163.com> References: <20260811073332.1351893-1-sh_def@163.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: cu1uz14o8ah6mzd8xsgc5499xkk5rbpd X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: C2CAA20004 X-HE-Tag: 1786498156-177964 X-HE-Meta: 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 ysY38TZz 5cULChoy42a3o0NiqDf0uXLosW770RiR2QKhxMoORvBkOVmCI85W7vMkmsZiDSee35F7LXw8Zhmpa17uDT9a3H3dIdUvZCM+b4TTDprpaG7r+Lch6R9qv/UGrKfpNwBICNX6dTnjvx5f9L+mhn1kYS4ATYXUpbsOuGcJ871pjI6Gh1ezXnNy6E/sCJoqOYNqUyNv0RheJRNoko9wjKFliwCS7qmiqSq2fhipZ3poeKNJCMHZEyqQ0VH54yyjLHvvvIQ2c/rs2QfhbM+kw9gP8VfR08E5DzsHSaFIJfBRkEkr5bQS/5BUh5uz1XzA/Cdq2+ekJJm78FyerLvftM+tlRCz98B1hPCBaFXZB0lUq7hp/5T1Rryq/uhesVjbgipKSD8B79LGVG9inT87ULZq+MoazoGODwRnsS0HcmFq+YBgwC/hD3ycg2W37MjuNcKFwtSyRxcptuLtnNXE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 11 Aug 2026 15:33:32 +0800 Hui Su wrote: > quarantine_size tracks the total number of bytes stored in > global_quarantine[]. It is incremented when per-CPU quarantine objects > are moved into the global quarantine and decremented when a global > batch is evicted by kasan_quarantine_reduce(). > > kasan_quarantine_remove_cache() also removes objects from the global > quarantine. qlist_move_cache() rebuilds the source batch and updates > its .bytes field, but quarantine_size is not adjusted accordingly. > > As a result, quarantine_size remains over-counted by the size of the > removed objects. The stale accounting accumulates across cache removals. > Once the inflated value exceeds quarantine_max_size, > kasan_quarantine_reduce() can evict a batch even though the actual > number of bytes in global_quarantine[] is still below > quarantine_max_size, shortening the quarantine window. > > Fix the accounting by recording each batch's size before > qlist_move_cache() and subtracting the number of bytes actually removed > from quarantine_size while holding quarantine_lock. > > A KUnit reproducer used during testing observed the over-count grow by > 4698864 bytes after one kasan_quarantine_remove_cache() call with the > fix reverted. With this change applied, the over-count did not grow. > Thanks. > @@ -365,9 +365,14 @@ void kasan_quarantine_remove_cache(struct kmem_cache *cache) Sashiko might have found an unrelated pre-existing bug in here. https://sashiko.dev/#/patchset/20260811073332.1351893-1-sh_def@163.com