linux-kernel - [PATCH 5.13 017/151] cifs: use the correct max-length for dentry_path

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Date:   Mon, 16 Aug 2021 15:00:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xiaoli Feng <xifeng@...hat.com>,
        Brian foster <bfoster@...hat.com>,
        "Paulo Alcantara (SUSE)" <pc@....nz>,
        Ronnie Sahlberg <lsahlber@...hat.com>,
        Steve French <stfrench@...rosoft.com>
Subject: [PATCH 5.13 017/151] cifs: use the correct max-length for dentry_path_raw()

From: Ronnie Sahlberg <lsahlber@...hat.com>

commit 981567bd965329df7e64b13e92a54da816c1e0a4 upstream.

RHBZ: 1972502

PATH_MAX is 4096 but PAGE_SIZE can be >4096 on some architectures
such as ppc and would thus write beyond the end of the actual object.

Cc: <stable@...r.kernel.org>
Reported-by: Xiaoli Feng <xifeng@...hat.com>
Suggested-by: Brian foster <bfoster@...hat.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@....nz>
Signed-off-by: Ronnie Sahlberg <lsahlber@...hat.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/cifs/dir.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -112,7 +112,7 @@ build_path_from_dentry_optional_prefix(s
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH)
 		pplen = cifs_sb->prepath ? strlen(cifs_sb->prepath) + 1 : 0;
 
-	s = dentry_path_raw(direntry, page, PAGE_SIZE);
+	s = dentry_path_raw(direntry, page, PATH_MAX);
 	if (IS_ERR(s))
 		return s;
 	if (!s[1])	// for root we want "", not "/"