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Thu, 28 May 2026 05:29:36 -0700 (PDT) From: Pavitra Jha To: idryomov@gmail.com, Slava.Dubeyko@ibm.com Cc: ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Pavitra Jha Subject: [PATCH v2] ceph: fix OOB read in ceph_osdc_list_watchers via uncapped outdata_len Date: Thu, 28 May 2026 08:29:11 -0400 Message-ID: <20260528122911.813491-1-jhapavitra98@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <71578c12a1b9d37aa2a39c8d1415084e0dea9216.camel@ibm.com> References: <71578c12a1b9d37aa2a39c8d1415084e0dea9216.camel@ibm.com> 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" The OSD reply header field op->payload_len is wire-controlled and is copied directly into m->outdata_len[i] without any bounds check: m->outdata_len[i] =3D le32_to_cpu(op->payload_len); This value propagates unchecked to req->r_ops[0].outdata_len and is then used to set the decode boundary in ceph_osdc_list_watchers(): void *const end =3D p + req->r_ops[0].outdata_len; The actual data allocation is always exactly one page: ceph_alloc_page_vector(1, GFP_NOIO) ceph_osd_data_pages_init(..., PAGE_SIZE, ...) The messenger caps the copy to PAGE_SIZE bytes, but the decode window end is set from the uncapped wire value. A malicious OSD can send outdata_len=3D0x10000, causing _safe decoder boundary checks to pass while the physical reads cross the slab allocation boundary. KASAN report (kernel 7.0.0-rc7, QEMU/x86_64, KASLR disabled): =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 BUG: KASAN: slab-out-of-bounds in ceph_oob2_init+0x23d/0xff0 [ceph_oob2_p= oc] Read of size 4 at addr ffff88800a229f9e by task insmod/57 CPU: 0 UID: 0 PID: 57 Comm: insmod Tainted: G O 7.0.0-rc= 7-g9c2abf69da83-dirty #15 PREEMPT(lazy) Tainted: [O]=3DOOT_MODULE Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian= -1.17.0-1 04/01/2014 Call Trace: dump_stack_lvl+0x4d/0x70 print_report+0x170/0x4f3 ? __pfx__raw_spin_lock_irqsave+0x10/0x10 kasan_report+0xda/0x110 ? ceph_oob2_init+0x23d/0xff0 [ceph_oob2_poc] ? ceph_oob2_init+0x23d/0xff0 [ceph_oob2_poc] ? __pfx_ceph_oob2_init+0x10/0x10 [ceph_oob2_poc] ceph_oob2_init+0x23d/0xff0 [ceph_oob2_poc] do_one_initcall+0x9a/0x3a0 ? __pfx_do_one_initcall+0x10/0x10 ? kasan_unpoison+0x44/0x70 do_init_module+0x27c/0x790 ? __pfx_do_init_module+0x10/0x10 ? __kasan_slab_free+0x47/0x70 ? kfree+0x15f/0x3b0 load_module+0x4a9a/0x6350 ? __pfx_load_module+0x10/0x10 ? security_file_permission+0x24/0x50 ? kernel_read_file+0x2ed/0x770 ? init_module_from_file+0x15c/0x180 init_module_from_file+0x15c/0x180 ? __pfx_init_module_from_file+0x10/0x10 ? tick_nohz_handler+0x2a3/0x640 ? _raw_spin_lock+0x7e/0xd0 idempotent_init_module+0x21f/0x750 ? __pfx_idempotent_init_module+0x10/0x10 ? fdget+0x4e/0x4a0 ? fdget+0x4e/0x4a0 __x64_sys_finit_module+0xba/0x120 do_syscall_64+0xe2/0x570 ? exc_page_fault+0x66/0xb0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Allocated by task 57: kasan_save_stack+0x30/0x50 kasan_save_track+0x14/0x30 __kasan_kmalloc+0x7f/0x90 ceph_oob2_init+0x44/0xff0 [ceph_oob2_poc] do_one_initcall+0x9a/0x3a0 do_init_module+0x27c/0x790 load_module+0x4a9a/0x6350 init_module_from_file+0x15c/0x180 idempotent_init_module+0x21f/0x750 __x64_sys_finit_module+0xba/0x120 do_syscall_64+0xe2/0x570 entry_YSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff88800a229000 which belongs to the cache kmalloc-4k of size 4096 The buggy address is located 3998 bytes inside of allocated 4000-byte region [ffff88800a229000, ffff88800a229fa0) Memory state around the buggy address: ffff88800a229e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88800a229f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff88800a229f80: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc ^ ffff88800a22a000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88800a22a080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc =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 val=3D0xccccaaaa (OOB garbage from KASAN redzone) Fix by introducing buf_len to hold the allocation size, using it in both ceph_osd_data_pages_init() and the min_t() decode boundary cap, so the two are guaranteed to stay in sync if the buffer size changes. Attacker model: a malicious or compromised OSD in a multi-tenant Ceph deployment can trigger this against any client issuing CEPH_OSD_OP_LIST_WATCHERS without further privileges beyond OSD session establishment. Fixes: a4ed38d7a180 ("libceph: support for CEPH_OSD_OP_LIST_WATCHERS") Cc: stable@vger.kernel.org Signed-off-by: Pavitra Jha --- v2: Introduce buf_len variable instead of hardcoding PAGE_SIZE independently in ceph_osd_data_pages_init() and the min_t() cap, per Viacheslav Dubeyko's review. --- net/ceph/osd_client.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c index a67093cf4..7545d3608 100644 --- a/net/ceph/osd_client.c +++ b/net/ceph/osd_client.c @@ -5063,6 +5063,7 @@ int ceph_osdc_list_watchers(struct ceph_osd_client *o= sdc, struct ceph_osd_request *req; struct page **pages; int ret; + const size_t buf_len =3D PAGE_SIZE; =20 req =3D ceph_osdc_alloc_request(osdc, NULL, 1, false, GFP_NOIO); if (!req) @@ -5081,7 +5082,7 @@ int ceph_osdc_list_watchers(struct ceph_osd_client *o= sdc, osd_req_op_init(req, 0, CEPH_OSD_OP_LIST_WATCHERS, 0); ceph_osd_data_pages_init(osd_req_op_data(req, 0, list_watchers, response_data), - pages, PAGE_SIZE, 0, false, true); + pages, buf_len, 0, false, true); =20 ret =3D ceph_osdc_alloc_messages(req, GFP_NOIO); if (ret) @@ -5091,7 +5092,7 @@ int ceph_osdc_list_watchers(struct ceph_osd_client *o= sdc, ret =3D ceph_osdc_wait_request(osdc, req); if (ret >=3D 0) { void *p =3D page_address(pages[0]); - void *const end =3D p + min_t(u32, req->r_ops[0].outdata_len, PAGE_SIZE); + void *const end =3D p + min_t(u32, req->r_ops[0].outdata_len, buf_len); =20 ret =3D decode_watchers(&p, end, watchers, num_watchers); } --=20 2.53.0