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 7555A1E6DDE for ; Wed, 4 Sep 2024 19:58:45 +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=1725479925; cv=none; b=skyu8V9jdLxw8njZxvkL5wyfGUtkWKMJUsCCpJuIT10E5sKBc5r9dmvW97tQSHypAakq3uw6iiuvtUc9EZtYYUKiISGY2hbkUfKp2ICRL8q+xdh7rcfGwpmZ7PmzSMR7qT4nBpMYw/lMxt5WeVOtSUKs+wIcquYfmYdkVEZ32gk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725479925; c=relaxed/simple; bh=NlKYTx5938KRpChHOYuJIBetxLJSV0LGk9YS6zvzfZI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=TBTSGbcCBd+Vh7/4I1/MXgoA2oogKrzhUK1/7lrsYXVGKvA69thUn9k9AlHBLmfQutEfRw2mJ/PEE+xvMIGNpi1tQPhGQL0P6qsvlsze8H365m04XQztFZPNbmlc374qE0TSM0X9560uQ9V0qmy7JyeCmH+/PcHMjtyMwuLYAGw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zUEbkBnd; 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="zUEbkBnd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F1A01C4CEC8; Wed, 4 Sep 2024 19:58:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1725479925; bh=NlKYTx5938KRpChHOYuJIBetxLJSV0LGk9YS6zvzfZI=; h=From:To:Cc:Subject:Date:Reply-to:From; b=zUEbkBnd+NCxk2UcOZHbSj4XpbMke+AYHLAJ2pDciBVG4wd6yl7TYYW/Gex98A/Zu Q5PtmiPIY0+c89RIjrNX8cKQ5h0MNHjbgMQKFMJCZ7tS+Ui7STCIw/4Ujz0nJSl7Nr NWHEb0Qq+e5oAnU50Luu7go+GbB5mE8Ecwq5MsPE= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2024-45000: fs/netfs/fscache_cookie: add missing "n_accesses" check Date: Wed, 4 Sep 2024 21:57:05 +0200 Message-ID: <2024090449-CVE-2024-45000-fd6f@gregkh> X-Mailer: git-send-email 2.46.0 Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Reply-to: , X-Developer-Signature: v=1; a=openpgp-sha256; l=5385; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=NlKYTx5938KRpChHOYuJIBetxLJSV0LGk9YS6zvzfZI=; b=owGbwMvMwCRo6H6F97bub03G02pJDGk3djexX444lhPB+ceKw6XHwU/88sYS6xOCFWtOcQbzR /6RM1jREcvCIMjEICumyPJlG8/R/RWHFL0MbU/DzGFlAhnCwMUpABNp9WVY0OaSaPDedPKyr8s+ K03hWSEzr7MplmF+mF6xUYJ6cOy0Pb8OHHdec+lC9OfjAA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit Description =========== In the Linux kernel, the following vulnerability has been resolved: fs/netfs/fscache_cookie: add missing "n_accesses" check This fixes a NULL pointer dereference bug due to a data race which looks like this: BUG: kernel NULL pointer dereference, address: 0000000000000008 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI CPU: 33 PID: 16573 Comm: kworker/u97:799 Not tainted 6.8.7-cm4all1-hp+ #43 Hardware name: HP ProLiant DL380 Gen9/ProLiant DL380 Gen9, BIOS P89 10/17/2018 Workqueue: events_unbound netfs_rreq_write_to_cache_work RIP: 0010:cachefiles_prepare_write+0x30/0xa0 Code: 57 41 56 45 89 ce 41 55 49 89 cd 41 54 49 89 d4 55 53 48 89 fb 48 83 ec 08 48 8b 47 08 48 83 7f 10 00 48 89 34 24 48 8b 68 20 <48> 8b 45 08 4c 8b 38 74 45 49 8b 7f 50 e8 4e a9 b0 ff 48 8b 73 10 RSP: 0018:ffffb4e78113bde0 EFLAGS: 00010286 RAX: ffff976126be6d10 RBX: ffff97615cdb8438 RCX: 0000000000020000 RDX: ffff97605e6c4c68 RSI: ffff97605e6c4c60 RDI: ffff97615cdb8438 RBP: 0000000000000000 R08: 0000000000278333 R09: 0000000000000001 R10: ffff97605e6c4600 R11: 0000000000000001 R12: ffff97605e6c4c68 R13: 0000000000020000 R14: 0000000000000001 R15: ffff976064fe2c00 FS: 0000000000000000(0000) GS:ffff9776dfd40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000008 CR3: 000000005942c002 CR4: 00000000001706f0 Call Trace: ? __die+0x1f/0x70 ? page_fault_oops+0x15d/0x440 ? search_module_extables+0xe/0x40 ? fixup_exception+0x22/0x2f0 ? exc_page_fault+0x5f/0x100 ? asm_exc_page_fault+0x22/0x30 ? cachefiles_prepare_write+0x30/0xa0 netfs_rreq_write_to_cache_work+0x135/0x2e0 process_one_work+0x137/0x2c0 worker_thread+0x2e9/0x400 ? __pfx_worker_thread+0x10/0x10 kthread+0xcc/0x100 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x30/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1b/0x30 Modules linked in: CR2: 0000000000000008 ---[ end trace 0000000000000000 ]--- This happened because fscache_cookie_state_machine() was slow and was still running while another process invoked fscache_unuse_cookie(); this led to a fscache_cookie_lru_do_one() call, setting the FSCACHE_COOKIE_DO_LRU_DISCARD flag, which was picked up by fscache_cookie_state_machine(), withdrawing the cookie via cachefiles_withdraw_cookie(), clearing cookie->cache_priv. At the same time, yet another process invoked cachefiles_prepare_write(), which found a NULL pointer in this code line: struct cachefiles_object *object = cachefiles_cres_object(cres); The next line crashes, obviously: struct cachefiles_cache *cache = object->volume->cache; During cachefiles_prepare_write(), the "n_accesses" counter is non-zero (via fscache_begin_operation()). The cookie must not be withdrawn until it drops to zero. The counter is checked by fscache_cookie_state_machine() before switching to FSCACHE_COOKIE_STATE_RELINQUISHING and FSCACHE_COOKIE_STATE_WITHDRAWING (in "case FSCACHE_COOKIE_STATE_FAILED"), but not for FSCACHE_COOKIE_STATE_LRU_DISCARDING ("case FSCACHE_COOKIE_STATE_ACTIVE"). This patch adds the missing check. With a non-zero access counter, the function returns and the next fscache_end_cookie_access() call will queue another fscache_cookie_state_machine() call to handle the still-pending FSCACHE_COOKIE_DO_LRU_DISCARD. The Linux kernel CVE team has assigned CVE-2024-45000 to this issue. Affected and fixed versions =========================== Issue introduced in 5.17 with commit 12bb21a29c19 and fixed in 6.1.107 with commit b8a50877f68e Issue introduced in 5.17 with commit 12bb21a29c19 and fixed in 6.6.48 with commit dfaa39b05a6c Issue introduced in 5.17 with commit 12bb21a29c19 and fixed in 6.10.7 with commit 0a4d41fa14b2 Issue introduced in 5.17 with commit 12bb21a29c19 and fixed in 6.11-rc4 with commit f71aa06398aa Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2024-45000 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/netfs/fscache_cookie.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/b8a50877f68efdcc0be3fcc5116e00c31b90e45b https://git.kernel.org/stable/c/dfaa39b05a6cf34a16c525a2759ee6ab26b5fef6 https://git.kernel.org/stable/c/0a4d41fa14b2a0efd40e350cfe8ec6a4c998ac1d https://git.kernel.org/stable/c/f71aa06398aabc2e3eaac25acdf3d62e0094ba70