From: Randy Dunlap rdunlap@infradead.org

stable inclusion from stable-5.10.36 commit 96fa26b74cdcf9f5c98996bf36bec9fb5b19ffe2 bugzilla: 189657 CVE: CVE-2021-46952

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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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 --- 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 29ec8b09a52d..05b39e8f97b9 100644 --- a/fs/nfs/fs_context.c +++ b/fs/nfs/fs_context.c @@ -937,6 +937,15 @@ static int nfs23_parse_monolithic(struct fs_context *fc, 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_fs_context, which nfs_fill_super * can deal with. @@ -1037,6 +1046,9 @@ static int nfs23_parse_monolithic(struct fs_context *fc,

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)