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NFS: fs_context: validate UDP retrans to prevent shift out-of-bounds

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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: 9954bf92c0 ("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>
This commit is contained in:
Randy Dunlap 2021-03-01 16:19:30 -08:00 committed by Trond Myklebust
parent f892c41c14
commit c09f11ef35
1 changed files with 12 additions and 0 deletions
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12
fs/nfs/fs_context.c
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@ -973,6 +973,15 @@ 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.
@ -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)