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b=n0zrOea4zxRr81GoybntTMpngg5CY97+QGQjJXCW15fLLvmN2WSpglK+GKEGxD8G6 cUN47XBfih/jGC5YaGdOl6t+n3NVDDxAJIwXyZlKrJe5imQdMwt4ZJ71aTnFNAvWml kgK84Q1a8EJg820kHD0M1dB627WZLDCgO5mCk1OxwWNIUpwW7/JLLJ34a7f+JjCwHt IOxwOWdEcGQVaOAOE857vQ+nbbPuk72dBuAFjMrz1p+tgJ11NMqPaFtyBtaznCVrpp yyvtUAUtwbh00bJXU8wpo3Cd3+b00yU/aYtc7dtcu0R12fgQb+tl4Hac0TRP6FPJRw FPOZN1IGKEfSA== From: Sasha Levin To: stable@vger.kernel.org, kartikey406@gmail.com Cc: syzbot+d8d4c31d40f868eaea30@syzkaller.appspotmail.com, Uladzislau Rezki , Hillf Danton , Andrew Morton , linux-mm@kvack.org Subject: FAILED: Patch "mm/vmalloc: prevent RCU stalls in kasan_release_vmalloc_node" failed to apply to 6.1-stable tree Date: Sat, 28 Feb 2026 20:43:59 -0500 Message-ID: <20260301014359.1706097-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 MIME-Version: 1.0 X-Patchwork-Hint: ignore X-stable: review Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 58F8E140004 X-Stat-Signature: nyfmnekdbmictps3ery68ak8ozmu83s3 X-Rspam-User: X-HE-Tag: 1772329442-676880 X-HE-Meta: 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 bWnHENg4 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 5747435e0fd474c24530ef1a6822f47e7d264b27 Mon Sep 17 00:00:00 2001 From: Deepanshu Kartikey Date: Mon, 12 Jan 2026 16:06:12 +0530 Subject: [PATCH] mm/vmalloc: prevent RCU stalls in kasan_release_vmalloc_node When CONFIG_PAGE_OWNER is enabled, freeing KASAN shadow pages during vmalloc cleanup triggers expensive stack unwinding that acquires RCU read locks. Processing a large purge_list without rescheduling can cause the task to hold CPU for extended periods (10+ seconds), leading to RCU stalls and potential OOM conditions. The issue manifests in purge_vmap_node() -> kasan_release_vmalloc_node() where iterating through hundreds or thousands of vmap_area entries and freeing their associated shadow pages causes: rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P6229/1:b..l ... task:kworker/0:17 state:R running task stack:28840 pid:6229 ... kasan_release_vmalloc_node+0x1ba/0xad0 mm/vmalloc.c:2299 purge_vmap_node+0x1ba/0xad0 mm/vmalloc.c:2299 Each call to kasan_release_vmalloc() can free many pages, and with page_owner tracking, each free triggers save_stack() which performs stack unwinding under RCU read lock. Without yielding, this creates an unbounded RCU critical section. Add periodic cond_resched() calls within the loop to allow: - RCU grace periods to complete - Other tasks to run - Scheduler to preempt when needed The fix uses need_resched() for immediate response under load, with a batch count of 32 as a guaranteed upper bound to prevent worst-case stalls even under light load. Link: https://lkml.kernel.org/r/20260112103612.627247-1-kartikey406@gmail.com Signed-off-by: Deepanshu Kartikey Reported-by: syzbot+d8d4c31d40f868eaea30@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=d8d4c31d40f868eaea30 Link: https://lore.kernel.org/all/20260112084723.622910-1-kartikey406@gmail.com/T/ [v1] Suggested-by: Uladzislau Rezki Reviewed-by: Uladzislau Rezki (Sony) Cc: Hillf Danton Cc: Signed-off-by: Andrew Morton --- mm/vmalloc.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 32d6ee92d4ff8..ca4c653286870 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2273,11 +2273,14 @@ decay_va_pool_node(struct vmap_node *vn, bool full_decay) reclaim_list_global(&decay_list); } +#define KASAN_RELEASE_BATCH_SIZE 32 + static void kasan_release_vmalloc_node(struct vmap_node *vn) { struct vmap_area *va; unsigned long start, end; + unsigned int batch_count = 0; start = list_first_entry(&vn->purge_list, struct vmap_area, list)->va_start; end = list_last_entry(&vn->purge_list, struct vmap_area, list)->va_end; @@ -2287,6 +2290,11 @@ kasan_release_vmalloc_node(struct vmap_node *vn) kasan_release_vmalloc(va->va_start, va->va_end, va->va_start, va->va_end, KASAN_VMALLOC_PAGE_RANGE); + + if (need_resched() || (++batch_count >= KASAN_RELEASE_BATCH_SIZE)) { + cond_resched(); + batch_count = 0; + } } kasan_release_vmalloc(start, end, start, end, KASAN_VMALLOC_TLB_FLUSH); -- 2.51.0