From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793821526; b=JSjKOvAmsus+V2loWnkYFMKJM4j56X4pTBCC6pUeplX8wAaWQUH3C4L2VZeX/iXxcXXk SLVZ95nJItn/YkMtuRzHtQhtGNOfs0B8/1yvD8fW+QC8+0Zylv9OcnSmZg7biUyQYfBBq Zm53GBfPgPXC/hCkqaMIrGpPg0uqu9/zMLlG7aPINwsBvxuLutP7XvSh+x423ubCreO7J HGoti+dwfvrg5PDiagtRzOFHuDnFAQE46PaN2C1ADnI2/lQMGwrx59h85M/ObUjQ5vg11 8CTLmy6iL7iry5CG37Sfod98pDL+ekZvNC8YN3aZ2qzfcaSzoUYab2d8OM5PwC9cwCw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793821526; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=27FbLy4q5yb0cOs41uRSsZFdq5FHyYVB3HtghgbCmpM=; b=Qs7fJzEmaKztVwfUOYwVZylIqOUHCpXR0OK2XD0negFqhuGZGTsVLhHSVuebJyRTKQLQ NJIvKjnJFnI1TSLMwV01cOfyY9/50DOinjxoJ05bPro+WvBNMEOJ/0vNkYWhE/+/tkEn9 ddbu3p3vaTNTI+plD6EiSjwhWELgX+E0QYJC3n8IVLkjQEogZZypmro9Bs9Vfr+BYWp/H g1i7w8QY4E/BKEPER0zD+D4sbzb1QnX/wstQWMp/DkfRcC7EZmoGeQFFARyJ2VuixCjOt 8XnUD+AmWGOCjdfspQdd7cYpoib5s4LNwbQ8Dae7j3m2mwkQJcF6IlWcsIeoaXRoQCw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=CNUBfgyW; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 49AB0608B6F4 for ; Wed, 4 Nov 2026 19:45:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=CNUBfgyW Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98AE11F00A1B; Wed, 4 Nov 2026 19:45:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793821526; bh=27FbLy4q5yb0cOs41uRSsZFdq5FHyYVB3HtghgbCmpM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=CNUBfgyWBfscFLu5ZG4ZSJ9N9J+s0prcQIAv1+tY6TRLbd5pv6uCwg0ER3Ds36E/9 Pq94wmykb7Qg5L5CEv3J9GuE1nB0fEIfhvYS0PKivNCxg2Xzz14aG7lad0VlrIAVh2 TkKoMzn7pk0J1P1tW7dJbkjQfo6y0HylEv60XB8fN9QUOd2PVWj5raKi++qGet4zRx hhGwb/tNgpajKE+RGly/Hu2QGPespbYALmFhKeEw0XSqF/q29OQwx13KDi8l7yQ512 pInF8T7xPF9e3aw5/jzT3dbRy4Bs90D3J6Y6u0N8rZthVb26oQFds1r3tPT0nzn3GS DGQRYSjijZwcw== From: Sasha Levin To: stable@vger.kernel.org Cc: Diego Oliva , David Howells , Paulo Alcantara , Sasha Levin Subject: [PATCH 5.15.y 3/3] smb: client: fix use-after-free infoleak via the readdir resume name Date: Wed, 4 Nov 2026 14:45:22 -0500 Message-ID: <20261104194436.333741-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261104194436.333741-1-sashal@kernel.org> References: <2026110403-submersed-uncloak-dc0a@gregkh> <20261104194436.333741-1-sashal@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Diego Oliva [ Upstream commit 59131dd72f62b198fc9ea1489ad9d3573154f684 ] CIFSFindNext() copies the resume name that cifs_save_resume_key() recorded from the last entry of the previous response into its request; psrch_inf->presume_name points into the response buffer that entry came from, and nothing ever clears it. find_cifs_entry() records a new name only from a response with a usable last entry, and cifs_readdir() only from an entry it walks to, so a response that carries no entries and leaves last_entry NULL, because CIFSFindFirst() or CIFSFindNext() rejected LastNameOffset, refreshes neither and presume_name keeps pointing into the previous response. That buffer has already been released: by CIFSFindNext() before it installs the new response, or by find_cifs_entry() when it rewinds the search, which does not drop the name either and can then fail in initiate_cifs_search() before a new response replaces it. The next CIFSFindNext() then copies up to PATH_MAX - 1 bytes of the resume name out of the released buffer into its request and sends them to the server: a use-after-free read that leaks kernel memory to a malicious or compromised server, which can provoke it with a single FindNext response that carries no entries and a LastNameOffset above CIFSMaxBufSize, which is all the existing check rejects. With KASAN enabled, a server that answers a listing that way gives: CIFS: VFS: ignoring corrupt resume name ================================================================== BUG: KASAN: slab-use-after-free in CIFSFindNext+0x8ca/0x14c0 Read of size 4080 at addr ffff88807c823f98 by task ls/83 CPU: 0 UID: 0 PID: 83 Comm: ls Tainted: G B 7.3.0-rc4-00457-gf14572c203d5 #69 PREEMPT(lazy) Tainted: [B]=BAD_PAGE Call Trace: kasan_report+0xdf/0x1a0 kasan_check_range+0x10f/0x1e0 __asan_memcpy+0x23/0x60 CIFSFindNext+0x8ca/0x14c0 cifs_readdir+0xf51/0x29c0 iterate_dir+0x1c0/0x570 __x64_sys_getdents64+0x133/0x270 do_syscall_64+0x109/0x5d0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Allocated by task 83 on cpu 1 at 13.497119s: cifs_buf_get+0x36/0x90 smb_init+0x4f/0x110 CIFSFindNext+0xf7/0x14c0 cifs_readdir+0xf51/0x29c0 Freed by task 83 on cpu 0 at 13.584018s: cifs_buf_release+0x41/0x80 CIFSFindNext+0xfce/0x14c0 cifs_readdir+0xf51/0x29c0 The buggy address is located 16280 bytes inside of freed 16588-byte region [ffff88807c820000, ffff88807c8240cc) ================================================================== The same memcpy() first reads past the end of that object while it is still live, a slab-out-of-bounds read that the following patches bound; that is the taint the report above carries. SMB1 is not negotiated by default; reaching this code requires an explicit vers=1.0 mount. Clear presume_name and resume_name_len whenever a new response is installed and when the rewind path releases the search buffer, so that the name never outlives the buffer it points into, and reset resume_key with them, since it was taken from the same entry and would otherwise be sent with an empty name. A response without a usable last entry then continues the search with an empty resume name rather than a stale one; CIFSFindNext() skips the copy of a zero-length name so that it never runs on the NULL pointer. The next patch in the series leaves last_entry NULL for a response that carries no entries, and bounds LastNameOffset against the received response rather than against CIFSMaxBufSize. Responses that are given a last entry today then take the path fixed here, so that patch must not be applied without this one. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Fixes: b77d753c413e ("[CIFS] Check that last search entry resume key is valid") Cc: stable@vger.kernel.org Assisted-by: Bynario AI Signed-off-by: Diego Oliva Reviewed-by: David Howells Signed-off-by: Paulo Alcantara Signed-off-by: Sasha Levin --- fs/cifs/cifssmb.c | 11 ++++++++++- fs/cifs/readdir.c | 3 +++ 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c index 5b1fb3216f238..6dc0b1793cbc7 100644 --- a/fs/cifs/cifssmb.c +++ b/fs/cifs/cifssmb.c @@ -4465,6 +4465,9 @@ CIFSFindFirst(const unsigned int xid, struct cifs_tcon *tcon, psrch_inf->entries_in_buffer = le16_to_cpu(parms->SearchCount); psrch_inf->index_of_last_entry = 2 /* skip . and .. */ + psrch_inf->entries_in_buffer; + psrch_inf->presume_name = NULL; + psrch_inf->resume_name_len = 0; + psrch_inf->resume_key = 0; lnoff = le16_to_cpu(parms->LastNameOffset); if (CIFSMaxBufSize < lnoff) { cifs_dbg(VFS, "ignoring corrupt resume name\n"); @@ -4528,7 +4531,10 @@ int CIFSFindNext(const unsigned int xid, struct cifs_tcon *tcon, name_len = psrch_inf->resume_name_len; params += name_len; if (name_len < PATH_MAX) { - memcpy(pSMB->ResumeFileName, psrch_inf->presume_name, name_len); + if (name_len) { + memcpy(pSMB->ResumeFileName, + psrch_inf->presume_name, name_len); + } byte_count += name_len; /* 14 byte parm len above enough for 2 byte null terminator */ pSMB->ResumeFileName[name_len] = 0; @@ -4583,6 +4589,9 @@ int CIFSFindNext(const unsigned int xid, struct cifs_tcon *tcon, psrch_inf->endOfSearch = !!parms->EndofSearch; psrch_inf->entries_in_buffer = le16_to_cpu(parms->SearchCount); psrch_inf->index_of_last_entry += psrch_inf->entries_in_buffer; + psrch_inf->presume_name = NULL; + psrch_inf->resume_name_len = 0; + psrch_inf->resume_key = 0; lnoff = le16_to_cpu(parms->LastNameOffset); if (CIFSMaxBufSize < lnoff) { cifs_dbg(VFS, "ignoring corrupt resume name\n"); diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c index 7c47a03afbcc3..cf099fce9ba1a 100644 --- a/fs/cifs/readdir.c +++ b/fs/cifs/readdir.c @@ -766,6 +766,9 @@ find_cifs_entry(const unsigned int xid, struct cifs_tcon *tcon, loff_t pos, cfile->srch_inf.ntwrk_buf_start = NULL; cfile->srch_inf.srch_entries_start = NULL; cfile->srch_inf.last_entry = NULL; + cfile->srch_inf.presume_name = NULL; + cfile->srch_inf.resume_name_len = 0; + cfile->srch_inf.resume_key = 0; } rc = initiate_cifs_search(xid, file, full_path); if (rc) { -- 2.53.0