From nobody Sun May 24 19:33:08 2026 Received: from mail-pf1-f181.google.com (mail-pf1-f181.google.com [209.85.210.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C21C337F8D0 for ; Sat, 23 May 2026 08:59:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.181 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779526786; cv=none; b=Ciqw4TgWXgCPvsY6UMj3AvtdF4eiAEROiTvvv4ws96axD6DJuQmxBw9X11eHdGATZ4AAHX+YQta1e6dE14aoFm1LxUx69kW7Q3wvh2GG1IpvLhQbY/FTawWb/KaGOA74OWvdxmMDY9686LY8eWDAioWgtLuEINCEkOzzHDP4k5M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779526786; c=relaxed/simple; bh=JVNLwiPtXCyMV1uRjjpMghimPebbtQ44GeZ/L5I6yMI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=QFpHDeZkh48dAS6bt7PL2+2Qx3SgBQ+OEQ06c9aHMqB3OO6VOiUYqjkcjltCsEbdjn2kuLfAlzBFjuFz9CSRQFTZXXd6iKaChVPpCmAMP4S+Gx8hmlQhzslSE5nsTzjLYWVDsoXj/iK8x0zzBJXNMGxcmUATOT9q18lqNblmP+8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=H/PWrlph; arc=none smtp.client-ip=209.85.210.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="H/PWrlph" Received: by mail-pf1-f181.google.com with SMTP id d2e1a72fcca58-83dc08db8e0so458531b3a.3 for ; Sat, 23 May 2026 01:59:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1779526784; x=1780131584; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=cvyRGKblMsa85uNp1iOm2E+XE8wdYLKtD/IRDH9iso4=; b=H/PWrlph2jVfux0bnLqrNUuOu/Oa6PZpjwffR3wsXrYoIZTqVM2enQ9aijwC3v98mg pnXJFEHhshwJAY+riflVAW8Tqtx9eTYfA/2h6PXaAsqRD6/B7YfRaqO0Bl8yCf7/iNmQ ith0w4BCSdjaVDlLQy4c9HrKz8UejVJSdO6+q4SfU1J7NP4Go35bMeSgrlMidI8vLbvz g5NIwzDmk74j7u/zpa4uPRZ4jHIpbEI34zhsXR8i6weTQ01OqO+EQFsAbyJlJT6U6bm/ qXX69IWRNVPNSe4vrYwCNWaSMajcgDGXS5ZlrLLajpG0aZHJ7+BA2seoCAYvZSGPzm4M ol/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779526784; x=1780131584; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=cvyRGKblMsa85uNp1iOm2E+XE8wdYLKtD/IRDH9iso4=; b=CW53xFfAo51EcBR42oDSw5Mpv/TuEKuaX+pagigw1qgwsm4yCe7DtEtpLbwr0k+sS5 RErQpnKd0kRi6tHoxBmqB+4Aq+4LND63AE7cROTa3m4NGLXkXKGRAzYJJKXpzxmucw/P xx4oV8KCM0A32b0X/NWOzxa4y2NcMHJ4f2H6AvPcEpyc5aRTYGy2g+IxhuDF05Z/xdi2 /hTAe3pTEB2HoII+o4BZXPTQ5QpcPS6vSWKJPt7qMjrjheGyHfQCL2eJl9q9iOeGySj5 WXpma2tByp2vneSII74A2nAkLUW2pEagtvwB3zxz57Oj4WQyd+Ym2MTOGiFzKRmMbCHT imbQ== X-Forwarded-Encrypted: i=1; AFNElJ++5O1lwv9++MjH7tVLzbZUar3VOEXc64ghZCRgbi9Jn3U3Nu2wSXHWXEgfztT+7MPOLcPreVjebSIoOIU=@vger.kernel.org X-Gm-Message-State: AOJu0YxZ7wyK0ap8jPSXXVhCTxuOr3aWgt8JsVEElrCAuwbD5NDGT1aO u7L1Xo1IVYankzgUELG+v1R2/SlUH0zyqhaqqMZWnG1tsUO++xrTwdr0 X-Gm-Gg: Acq92OHkzVrf87wuKxqW2SbrKdiSKF+QjKPjmgYHb90voXoHgwUb4hdiLROFrbiDS+d yOAFduM7r4rrEnmv76gfACUB1i2JTga/gxFe5PcWHPsDGlpOsjT9T8ipJSAXJF7+ZZfpXAiH7WU ioKCEwR0caClhwIYpH+v4PU2TQ33ocgn69eUXjjbacvnrx9ycQsFjgNNtzWj2QokK47HaVB+bNO Sqobd2IO7D2LHv34xUOf1z9huOkbuyPlfc5cQhxy+qXjwzdiLZWtZllzWPJ9E+3dCKlD3aooUh6 IpxF/KX0dJVEdxIvGRhAj1+XJoaXQniKIj+8uPmODXrb85QDl0KX8TLlKla3ZC++hDBsW7StVBh WhKuV0PBsqi38iHGLOO3I44WQI67tbEWv904cUMnYLVqLUAkHFe9j769NbTokE6laCeGDSRLuXO UjsXnB0f0+o9f5c/XN45A04uQFM44= X-Received: by 2002:a05:6a21:4c11:b0:3b3:cff:cb54 with SMTP id adf61e73a8af0-3b328cde60emr3597088637.2.1779526783906; Sat, 23 May 2026 01:59:43 -0700 (PDT) Received: from kali ([2402:e280:3d7c:a2:536a:b505:93f5:9d5d]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84164b0427bsm4696739b3a.22.2026.05.23.01.59.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 23 May 2026 01:59:43 -0700 (PDT) From: Pavitra Jha To: idryomov@gmail.com Cc: amarkuze@redhat.com, slava@dubeyko.com, ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Pavitra Jha Subject: [PATCH] ceph: fix multiple unsafe decodes in decode_locker() Date: Sat, 23 May 2026 04:59:02 -0400 Message-ID: <20260523085902.502821-1-jhapavitra98@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" decode_locker() in cls_lock_client.c contains three unsafe decode operations that allow a malicious or compromised OSD to trigger slab-out-of-bounds reads: 1. ceph_decode_copy() at the locker_id_t name field has no preceding bounds check. With p =3D=3D end after ceph_start_decoding() accepts struct_len=3D0, this reads sizeof(ceph_entity_name) =3D 9 bytes past the validated buffer boundary. 2. *p +=3D sizeof(struct ceph_timespec) after the locker_info_t header is an unchecked pointer advance. A malicious OSD can position p past end, causing all subsequent _safe checks to pass against a bogus boundary. 3. len =3D ceph_decode_32(p) has no preceding bounds check, and the immediately following *p +=3D len is uncapped. A malicious OSD can send len=3D0xffffffff, advancing p gigabytes past end and escaping the decode window entirely. Fix all three by replacing bare operations with their safe variants: ceph_decode_copy -> ceph_decode_copy_safe *p +=3D sizeof(...) -> ceph_decode_skip_n ceph_decode_32(p) -> ceph_decode_32_safe *p +=3D len -> ceph_decode_skip_n A new bad: label is added to return -EINVAL on any bounds violation. KASAN report (kernel 7.0.0-rc7, QEMU/x86_64, KASLR disabled): [ 26.183969] ceph_oob4_poc: buf=3Dffff888009e31000 end=3Dffff888009e31f= a0 [ 26.186087] ceph_oob4_poc: struct_v=3D1 struct_len=3D0 p=3D=3Dend: 1 [ 26.186738] ceph_oob4_poc: triggering bare ceph_decode_32 past slab bo= undary... [ 26.187679] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D [ 26.188236] BUG: KASAN: slab-out-of-bounds in ceph_oob4_init+0x22b/0xf= f0 [ceph_oob4_poc] [ 26.188236] Read of size 4 at addr ffff888009e31fa0 by task insmod/59 [ 26.188236] CPU: 0 UID: 0 PID: 59 Comm: insmod Tainted: G O = 7.0.0-rc7-g9c2abf69da83-dirty #15 PREEMPT(lazy) [ 26.188236] Tainted: [O]=3DOOT_MODULE [ 26.188236] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIO= S 1.17.0-debian-1.17.0-1 04/01/2014 [ 26.188236] Call Trace: [ 26.188236] [ 26.188236] dump_stack_lvl+0x4d/0x70 [ 26.188236] print_report+0x170/0x4f3 [ 26.188236] ? __pfx__raw_spin_lock_irqsave+0x10/0x10 [ 26.188236] kasan_report+0xda/0x110 [ 26.188236] ? ceph_oob4_init+0x22b/0xff0 [ceph_oob4_poc] [ 26.188236] ? ceph_oob4_init+0x22b/0xff0 [ceph_oob4_poc] [ 26.188236] ? __pfx_ceph_oob4_init+0x10/0x10 [ceph_oob4_poc] [ 26.188236] ceph_oob4_init+0x22b/0xff0 [ceph_oob4_poc] [ 26.188236] do_one_initcall+0x9a/0x3a0 [ 26.188236] ? __pfx_do_one_initcall+0x10/0x10 [ 26.188236] do_init_module+0x27c/0x790 [ 26.188236] load_module+0x4a9a/0x6350 [ 26.188236] init_module_from_file+0x15c/0x180 [ 26.188236] idempotent_init_module+0x21f/0x750 [ 26.188236] __x64_sys_finit_module+0xba/0x120 [ 26.188236] do_syscall_64+0xe2/0x570 [ 26.188236] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 26.188236] [ 26.188236] The buggy address belongs to the object at ffff888009e31000 [ 26.188236] which belongs to the cache kmalloc-4k of size 4096 [ 26.188236] The buggy address is located 0 bytes to the right of [ 26.188236] allocated 4000-byte region [ffff888009e31000, ffff888009e= 31fa0) [ 26.188236] Memory state around the buggy address: [ 26.188236] ffff888009e31f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 = 00 00 00 [ 26.188236] >ffff888009e31f80: 00 00 00 00 fc fc fc fc fc fc fc fc fc = fc fc fc [ 26.188236] ^ [ 26.188236] ffff888009e32000: fc fc fc fc fc fc fc fc fc fc fc fc fc = fc fc fc [ 26.188236] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D [ 26.255513] ceph_oob4_poc: len=3D0xcccccccc (OOB garbage from KASAN re= dzone) 0xCCCCCCCC is KASAN redzone poison, confirming the read landed in the slab redzone immediately past the 4000-byte allocation. Attacker model: a malicious or compromised OSD in a multi-tenant Ceph deployment can trigger this against any kernel client that issues the lock.get_info class method (e.g. during RBD exclusive lock acquisition) without any further privileges beyond OSD session establishment. Fixes: d4ed4a530562 ("libceph: support for lock.lock_info") Cc: stable@vger.kernel.org Signed-off-by: Pavitra Jha --- net/ceph/cls_lock_client.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/net/ceph/cls_lock_client.c b/net/ceph/cls_lock_client.c index 78276273c..00f0309a6 100644 --- a/net/ceph/cls_lock_client.c +++ b/net/ceph/cls_lock_client.c @@ -259,7 +259,7 @@ static int decode_locker(void **p, void *end, struct ce= ph_locker *locker) if (ret) return ret; =20 - ceph_decode_copy(p, &locker->id.name, sizeof(locker->id.name)); + ceph_decode_copy_safe(p, end, &locker->id.name, sizeof(locker->id.name), = bad); s =3D ceph_extract_encoded_string(p, end, NULL, GFP_NOIO); if (IS_ERR(s)) return PTR_ERR(s); @@ -270,19 +270,21 @@ static int decode_locker(void **p, void *end, struct = ceph_locker *locker) if (ret) return ret; =20 - *p +=3D sizeof(struct ceph_timespec); /* skip expiration */ + ceph_decode_skip_n(p, end, sizeof(struct ceph_timespec), bad); /* skip ex= piration */ =20 ret =3D ceph_decode_entity_addr(p, end, &locker->info.addr); if (ret) return ret; =20 - len =3D ceph_decode_32(p); - *p +=3D len; /* skip description */ + ceph_decode_32_safe(p, end, len, bad); + ceph_decode_skip_n(p, end, len, bad); /* skip description */ =20 dout("%s %s%llu cookie %s addr %s\n", __func__, ENTITY_NAME(locker->id.name), locker->id.cookie, ceph_pr_addr(&locker->info.addr)); return 0; +bad: + return -EINVAL; } =20 static int decode_lockers(void **p, void *end, u8 *type, char **tag, --=20 2.53.0