linux-kernel - Re: [PATCH v2] nfsd: clear acl_access/acl

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Message-ID: <173791790453.1645.17131731130789235526.b4-ty@oracle.com>
Date: Sun, 26 Jan 2025 13:59:06 -0500
From: cel@...nel.org
To: jlayton@...nel.org,
	neilb@...e.de,
	okorniev@...hat.com,
	Dai.Ngo@...cle.com,
	tom@...pey.com,
	Trond.Myklebust@...app.com,
	rick.macklem@...il.com,
	zhangjian496@...wei.com,
	linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Li Lingfeng <lilingfeng3@...wei.com>
Cc: Chuck Lever <chuck.lever@...cle.com>,
	yukuai1@...weicloud.com,
	houtao1@...wei.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	lilingfeng@...weicloud.com
Subject: Re: [PATCH v2] nfsd: clear acl_access/acl_default after releasing them

From: Chuck Lever <chuck.lever@...cle.com>

On Sun, 26 Jan 2025 17:47:22 +0800, Li Lingfeng wrote:
> If getting acl_default fails, acl_access and acl_default will be released
> simultaneously. However, acl_access will still retain a pointer pointing
> to the released posix_acl, which will trigger a WARNING in
> nfs3svc_release_getacl like this:
> 
> ------------[ cut here ]------------
> refcount_t: underflow; use-after-free.
> WARNING: CPU: 26 PID: 3199 at lib/refcount.c:28
> refcount_warn_saturate+0xb5/0x170
> Modules linked in:
> CPU: 26 UID: 0 PID: 3199 Comm: nfsd Not tainted
> 6.12.0-rc6-00079-g04ae226af01f-dirty #8
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> 1.16.1-2.fc37 04/01/2014
> RIP: 0010:refcount_warn_saturate+0xb5/0x170
> Code: cc cc 0f b6 1d b3 20 a5 03 80 fb 01 0f 87 65 48 d8 00 83 e3 01 75
> e4 48 c7 c7 c0 3b 9b 85 c6 05 97 20 a5 03 01 e8 fb 3e 30 ff <0f> 0b eb
> cd 0f b6 1d 8a3
> RSP: 0018:ffffc90008637cd8 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff83904fde
> RDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffff88871ed36380
> RBP: ffff888158beeb40 R08: 0000000000000001 R09: fffff520010c6f56
> R10: ffffc90008637ab7 R11: 0000000000000001 R12: 0000000000000001
> R13: ffff888140e77400 R14: ffff888140e77408 R15: ffffffff858b42c0
> FS:  0000000000000000(0000) GS:ffff88871ed00000(0000)
> knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000562384d32158 CR3: 000000055cc6a000 CR4: 00000000000006f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> 
> [...]

Applied to nfsd-testing, thanks!

[1/1] nfsd: clear acl_access/acl_default after releasing them
      commit: d5595d284a1c022b341bab2f66a631ae13eaee14

--
Chuck Lever