From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4F9CD22CBC6 for ; Thu, 20 Nov 2025 16:15:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763655332; cv=none; b=blV6e1qAnz6twNtbCrf8OllTBtLV4uC0f69vUAEHm4gIH9eg/9ZfsWxuQAxhr10+2yg5tASwqtmUvlbj2sdNT39MUUYaMMOI2myYs+pfC46qU0pRod+h5jfbhP+PIN9Kmkszvf4HVh2aP958EINYFH3+IX/uQETzMe5Y9h1CoQg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763655332; c=relaxed/simple; bh=H9flIl8a53bjWP7GTSG+GMxgq920SNB95/t98MZCeg0=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=YfcMJNe6HtsmWL+4pYTd2GbHH5p+QG1DWXESjKPopEgaLKG6NCFS0Du8ncXC/7AUsw90FdtvbWu64TnWDV3O8ZSMoa9p9MRCiercBvzc1PBNqItNgGU0RlPCnynYSuFzt5rSaCcb7NezQowofvshNnyzWfPiq27Y/2p5UOLoMAg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Coz3SfLh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Coz3SfLh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C3B0FC4CEF1; Thu, 20 Nov 2025 16:15:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1763655332; bh=H9flIl8a53bjWP7GTSG+GMxgq920SNB95/t98MZCeg0=; h=Subject:To:Cc:From:Date:From; b=Coz3SfLhNFeEGa8xnhqOAlSV/V4/O056HkYFzVLzXjbgawsoVCkeKohPCcRS7dSqP ejgAbBr+fibLpOQ1K0pwvh+0xB8GKjNK/h0AS+L/DnawZfpthokxAA5/sPWD08pVcy vgiz9iWeRQYSONQO0xNU++VFchVeumMefcEbIQ0w= Subject: FAILED: patch "[PATCH] crash: fix crashkernel resource shrink" failed to apply to 6.6-stable tree To: sourabhjain@linux.ibm.com,akpm@linux-foundation.org,bhe@redhat.com,stable@vger.kernel.org,thunder.leizhen@huawei.com Cc: From: Date: Thu, 20 Nov 2025 17:15:29 +0100 Message-ID: <2025112029-arrogance-bondless-6a5b@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-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 . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 00fbff75c5acb4755f06f08bd1071879c63940c5 # git commit -s git send-email --to '' --in-reply-to '2025112029-arrogance-bondless-6a5b@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 00fbff75c5acb4755f06f08bd1071879c63940c5 Mon Sep 17 00:00:00 2001 From: Sourabh Jain Date: Sun, 2 Nov 2025 01:07:41 +0530 Subject: [PATCH] crash: fix crashkernel resource shrink When crashkernel is configured with a high reservation, shrinking its value below the low crashkernel reservation causes two issues: 1. Invalid crashkernel resource objects 2. Kernel crash if crashkernel shrinking is done twice For example, with crashkernel=200M,high, the kernel reserves 200MB of high memory and some default low memory (say 256MB). The reservation appears as: cat /proc/iomem | grep -i crash af000000-beffffff : Crash kernel 433000000-43f7fffff : Crash kernel If crashkernel is then shrunk to 50MB (echo 52428800 > /sys/kernel/kexec_crash_size), /proc/iomem still shows 256MB reserved: af000000-beffffff : Crash kernel Instead, it should show 50MB: af000000-b21fffff : Crash kernel Further shrinking crashkernel to 40MB causes a kernel crash with the following trace (x86): BUG: kernel NULL pointer dereference, address: 0000000000000038 PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI Call Trace: ? __die_body.cold+0x19/0x27 ? page_fault_oops+0x15a/0x2f0 ? search_module_extables+0x19/0x60 ? search_bpf_extables+0x5f/0x80 ? exc_page_fault+0x7e/0x180 ? asm_exc_page_fault+0x26/0x30 ? __release_resource+0xd/0xb0 release_resource+0x26/0x40 __crash_shrink_memory+0xe5/0x110 crash_shrink_memory+0x12a/0x190 kexec_crash_size_store+0x41/0x80 kernfs_fop_write_iter+0x141/0x1f0 vfs_write+0x294/0x460 ksys_write+0x6d/0xf0 This happens because __crash_shrink_memory()/kernel/crash_core.c incorrectly updates the crashk_res resource object even when crashk_low_res should be updated. Fix this by ensuring the correct crashkernel resource object is updated when shrinking crashkernel memory. Link: https://lkml.kernel.org/r/20251101193741.289252-1-sourabhjain@linux.ibm.com Fixes: 16c6006af4d4 ("kexec: enable kexec_crash_size to support two crash kernel regions") Signed-off-by: Sourabh Jain Acked-by: Baoquan He Cc: Zhen Lei Cc: Signed-off-by: Andrew Morton diff --git a/kernel/crash_core.c b/kernel/crash_core.c index 3b1c43382eec..99dac1aa972a 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -373,7 +373,7 @@ static int __crash_shrink_memory(struct resource *old_res, old_res->start = 0; old_res->end = 0; } else { - crashk_res.end = ram_res->start - 1; + old_res->end = ram_res->start - 1; } crash_free_reserved_phys_range(ram_res->start, ram_res->end);