From c09f11ef35955785f92369e25819bf0629df2e59 Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Mon, 1 Mar 2021 16:19:30 -0800 Subject: [PATCH] NFS: fs_context: validate UDP retrans to prevent shift out-of-bounds Fix shift out-of-bounds in xprt_calc_majortimeo(). This is caused by a garbage timeout (retrans) mount option being passed to nfs mount, in this case from syzkaller. If the protocol is XPRT_TRANSPORT_UDP, then 'retrans' is a shift value for a 64-bit long integer, so 'retrans' cannot be >= 64. If it is >= 64, fail the mount and return an error. Fixes: 9954bf92c0cd ("NFS: Move mount parameterisation bits into their own file") Reported-by: syzbot+ba2e91df8f74809417fa@syzkaller.appspotmail.com Reported-by: syzbot+f3a0fa110fd630ab56c8@syzkaller.appspotmail.com Signed-off-by: Randy Dunlap Cc: Trond Myklebust Cc: Anna Schumaker Cc: linux-nfs@vger.kernel.org Cc: David Howells Cc: Al Viro Cc: stable@vger.kernel.org Signed-off-by: Trond Myklebust --- fs/nfs/fs_context.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c index 971a925..902db12 100644 --- a/fs/nfs/fs_context.c +++ b/fs/nfs/fs_context.c @@ -974,6 +974,15 @@ static int nfs23_parse_monolithic(struct fs_context *fc, sizeof(mntfh->data) - mntfh->size); /* + * for proto == XPRT_TRANSPORT_UDP, which is what uses + * to_exponential, implying shift: limit the shift value + * to BITS_PER_LONG (majortimeo is unsigned long) + */ + if (!(data->flags & NFS_MOUNT_TCP)) /* this will be UDP */ + if (data->retrans >= 64) /* shift value is too large */ + goto out_invalid_data; + + /* * Translate to nfs_fs_context, which nfs_fill_super * can deal with. */ @@ -1073,6 +1082,9 @@ out_no_address: out_invalid_fh: return nfs_invalf(fc, "NFS: invalid root filehandle"); + +out_invalid_data: + return nfs_invalf(fc, "NFS: invalid binary mount data"); } #if IS_ENABLED(CONFIG_NFS_V4) -- 2.7.4