From: Randy Dunlap rdunlap@infradead.org

stable inclusion from stable-5.10.36 commit 96fa26b74cdcf9f5c98996bf36bec9fb5b19ffe2 bugzilla: https://gitee.com/src-openeuler/kernel/issues/I949C5 CVE: CVE-2021-46952

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commit c09f11ef35955785f92369e25819bf0629df2e59 upstream.

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 rdunlap@infradead.org Cc: Trond Myklebust trond.myklebust@hammerspace.com Cc: Anna Schumaker anna.schumaker@netapp.com Cc: linux-nfs@vger.kernel.org Cc: David Howells dhowells@redhat.com Cc: Al Viro viro@zeniv.linux.org.uk Cc: stable@vger.kernel.org Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Conflicts: fs/nfs/fs_context.c Signed-off-by: ZhaoLong Wang wangzhaolong1@huawei.com --- fs/nfs/super.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)

diff --git a/fs/nfs/super.c b/fs/nfs/super.c index a05e1eb2c3fd..15f4e6d34fdd 100644 --- a/fs/nfs/super.c +++ b/fs/nfs/super.c @@ -2068,6 +2068,15 @@ static int nfs23_validate_mount_data(void *options, memset(mntfh->data + mntfh->size, 0, 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_parsed_mount_data, which nfs_fill_super * can deal with. @@ -2168,6 +2177,10 @@ static int nfs23_validate_mount_data(void *options, out_invalid_fh: dfprintk(MOUNT, "NFS: invalid root filehandle\n"); return -EINVAL; + +out_invalid_data: + dfprintk(MOUNT, "NFS: invalid binary mount data\n"); + return -EINVAL; }

#if IS_ENABLED(CONFIG_NFS_V4)