From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: [PATCH AUTOSEL 4.20 269/304] cifs: check ntwrk_buf_start for NULL before dereferencing it Date: Mon, 28 Jan 2019 10:43:06 -0500 Message-ID: <20190128154341.47195-269-sashal@kernel.org> References: <20190128154341.47195-1-sashal@kernel.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: Ronnie Sahlberg , Steve French , Sasha Levin , linux-cifs@vger.kernel.org To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Return-path: In-Reply-To: <20190128154341.47195-1-sashal@kernel.org> Sender: stable-owner@vger.kernel.org List-Id: linux-cifs.vger.kernel.org From: Ronnie Sahlberg [ Upstream commit 59a63e479ce36a3f24444c3a36efe82b78e4a8e0 ] RHBZ: 1021460 There is an issue where when multiple threads open/close the same directory ntwrk_buf_start might end up being NULL, causing the call to smbCalcSize later to oops with a NULL deref. The real bug is why this happens and why this can become NULL for an open cfile, which should not be allowed. This patch tries to avoid a oops until the time when we fix the underlying issue. Signed-off-by: Ronnie Sahlberg Signed-off-by: Steve French Signed-off-by: Sasha Levin --- fs/cifs/readdir.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c index e169e1a5fd35..3925a7bfc74d 100644 --- a/fs/cifs/readdir.c +++ b/fs/cifs/readdir.c @@ -655,7 +655,14 @@ find_cifs_entry(const unsigned int xid, struct cifs_tcon *tcon, loff_t pos, /* scan and find it */ int i; char *cur_ent; - char *end_of_smb = cfile->srch_inf.ntwrk_buf_start + + char *end_of_smb; + + if (cfile->srch_inf.ntwrk_buf_start == NULL) { + cifs_dbg(VFS, "ntwrk_buf_start is NULL during readdir\n"); + return -EIO; + } + + end_of_smb = cfile->srch_inf.ntwrk_buf_start + server->ops->calc_smb_size( cfile->srch_inf.ntwrk_buf_start, server); -- 2.19.1