Commit 254c1913 authored Dec 13, 2018 by Ronnie Sahlberg Committed by Greg Kroah-Hartman Feb 12, 2019

cifs: check ntwrk_buf_start for NULL before dereferencing it



[ 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 <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent b0d08e07

fs/cifs/readdir.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -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);