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=1793822090; b=Hu/Ohncr/Fe/klAxCtD1zUsWnq7QCPmY4p3AaYWrnFlL445P7g4fKasvVrORqmF6qNcu MxAASzhIXVRjq6NcV/r6kTO4d4xJEPa5pli+AsvpKAsmSe/gMm2M4ZcH2rY9mbvPVQkGH hZiNT0K7S7P8AD/Jo8GN/YoQ8HDjD2CgnkcpqJ4jAu2tOB2y6caPJf2OK7NiJv+SwzLtq IUuxsq9cYypVdfYTDvBx5JjF1kVGpmLsICqtwC9SSsCqwrwOcjM8AikLC2zmmipshw2Fd Hpf/oFAUvBd5VawZY7qHaL0ftYSqgluTNzKCwGdpvZrmnY3JkmhzlZ885bzWpSnQxtg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793822090; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=BE+w62NRPHyJ8tRdn1GuDNMJzwi0nKBDdFGcX9mWqik=; b=zustBmEl+teYUF57dgcCSbEXnTLO7CSY71umiG4bh6TB2bW6OTDWY4W6EW+vDOQHx/da DaxEVQT1U3arpun/zTKLAqsCRkU1eym/hzVaBvssdI6JH1RyJSYbdyoIogAKr7u6yk1fx rUnAv1OPKwUurSXKOCOMQ3DDrslQ2gIGOD3ENPGjRl+dIJw9MOBHpO5OiPXlyt6wW7r7Q T3oyXjmrgtwmzTak5CBfDY4PE7vu/v1Ou6QZnSe5H4ZiKlMOAkzns2vdtekWsC8sykbHx R8TbtvaHI8cbg11yR7gW/fDiRI8iwRvTNMC9mOChDIILkbNvZIhEixopuXsneFVlNZQ== 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=QEpBtidp; 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 D32D16099A06 for ; Wed, 4 Nov 2026 19:54:49 +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=QEpBtidp Received: by smtp.kernel.org (Postfix) with ESMTPSA id 295661F00A1A; Wed, 4 Nov 2026 19:54:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793822089; bh=BE+w62NRPHyJ8tRdn1GuDNMJzwi0nKBDdFGcX9mWqik=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=QEpBtidpHIBA6iLiZWZWb3puewynrAJn8/FQwFmT36+yW7WDVKUCuaO/9ZUBnO0SO XGyrw1xp4NQBYs33mzm0K7tTw7pM6NAJmRKwp1Gw+e8/dgJPev+NxuF0oDOk38VOMc et3hnfU+kt69DwxvYW/aLNT8ahF85fXl9AO5Poxf8agHAO4WwtQxckY+I2gfltA8uo Mb/Xag2Vwhj7vvDI/Bii58OY2pB+8KTqfmDm5MxUJAPwGgBGkixY5Cr3vQm/2ci8nU q//3RYFWeTJztx6MiwiLqeQDn45JN6hMhWeytmag+y2G6DdS2IABy0LWtsbgMagRdi Kw0f1veZkz/GQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Diego Oliva , David Howells , Paulo Alcantara , Sasha Levin Subject: [PATCH 5.10.y 3/3] smb: client: fix use-after-free infoleak via the readdir resume name Date: Wed, 4 Nov 2026 14:54:46 -0500 Message-ID: <20261104195419.360475-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261104195419.360475-1-sashal@kernel.org> References: <2026110404-moonrise-gnarly-7268@gregkh> <20261104195419.360475-1-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 7f0839d5c6db7..b823231e53ab5 100644 --- a/fs/cifs/cifssmb.c +++ b/fs/cifs/cifssmb.c @@ -4573,6 +4573,9 @@ 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"); @@ -4636,7 +4639,10 @@ 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; @@ -4691,6 +4697,9 @@ 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 9a7315aa24e0d..40005e7da5771 100644 --- a/fs/cifs/readdir.c +++ b/fs/cifs/readdir.c @@ -759,6 +759,9 @@ 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