lkml.org 
[lkml]   [2018]   [Jul]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.4 091/105] NFSv4: Fix possible 1-byte stack overflow in nfs_idmap_read_and_verify_message
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Dave Wysochanski <dwysocha@redhat.com>

    commit d68894800ec5712d7ddf042356f11e36f87d7f78 upstream.

    In nfs_idmap_read_and_verify_message there is an incorrect sprintf '%d'
    that converts the __u32 'im_id' from struct idmap_msg to 'id_str', which
    is a stack char array variable of length NFS_UINT_MAXLEN == 11.
    If a uid or gid value is > 2147483647 = 0x7fffffff, the conversion
    overflows into a negative value, for example:
    crash> p (unsigned) (0x80000000)
    $1 = 2147483648
    crash> p (signed) (0x80000000)
    $2 = -2147483648
    The '-' sign is written to the buffer and this causes a 1 byte overflow
    when the NULL byte is written, which corrupts kernel stack memory. If
    CONFIG_CC_STACKPROTECTOR_STRONG is set we see a stack-protector panic:

    [11558053.616565] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffffa05b8a8c
    [11558053.639063] CPU: 6 PID: 9423 Comm: rpc.idmapd Tainted: G W ------------ T 3.10.0-514.el7.x86_64 #1
    [11558053.641990] Hardware name: Red Hat OpenStack Compute, BIOS 1.10.2-3.el7_4.1 04/01/2014
    [11558053.644462] ffffffff818c7bc0 00000000b1f3aec1 ffff880de0f9bd48 ffffffff81685eac
    [11558053.646430] ffff880de0f9bdc8 ffffffff8167f2b3 ffffffff00000010 ffff880de0f9bdd8
    [11558053.648313] ffff880de0f9bd78 00000000b1f3aec1 ffffffff811dcb03 ffffffffa05b8a8c
    [11558053.650107] Call Trace:
    [11558053.651347] [<ffffffff81685eac>] dump_stack+0x19/0x1b
    [11558053.653013] [<ffffffff8167f2b3>] panic+0xe3/0x1f2
    [11558053.666240] [<ffffffff811dcb03>] ? kfree+0x103/0x140
    [11558053.682589] [<ffffffffa05b8a8c>] ? idmap_pipe_downcall+0x1cc/0x1e0 [nfsv4]
    [11558053.689710] [<ffffffff810855db>] __stack_chk_fail+0x1b/0x30
    [11558053.691619] [<ffffffffa05b8a8c>] idmap_pipe_downcall+0x1cc/0x1e0 [nfsv4]
    [11558053.693867] [<ffffffffa00209d6>] rpc_pipe_write+0x56/0x70 [sunrpc]
    [11558053.695763] [<ffffffff811fe12d>] vfs_write+0xbd/0x1e0
    [11558053.702236] [<ffffffff810acccc>] ? task_work_run+0xac/0xe0
    [11558053.704215] [<ffffffff811fec4f>] SyS_write+0x7f/0xe0
    [11558053.709674] [<ffffffff816964c9>] system_call_fastpath+0x16/0x1b

    Fix this by calling the internally defined nfs_map_numeric_to_string()
    function which properly uses '%u' to convert this __u32. For consistency,
    also replace the one other place where snprintf is called.

    Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
    Reported-by: Stephen Johnston <sjohnsto@redhat.com>
    Fixes: cf4ab538f1516 ("NFSv4: Fix the string length returned by the idmapper")
    Cc: stable@vger.kernel.org # v3.4+
    Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/nfs/nfs4idmap.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    --- a/fs/nfs/nfs4idmap.c
    +++ b/fs/nfs/nfs4idmap.c
    @@ -343,7 +343,7 @@ static ssize_t nfs_idmap_lookup_name(__u
    int id_len;
    ssize_t ret;

    - id_len = snprintf(id_str, sizeof(id_str), "%u", id);
    + id_len = nfs_map_numeric_to_string(id, id_str, sizeof(id_str));
    ret = nfs_idmap_get_key(id_str, id_len, type, buf, buflen, idmap);
    if (ret < 0)
    return -EINVAL;
    @@ -626,7 +626,8 @@ static int nfs_idmap_read_and_verify_mes
    if (strcmp(upcall->im_name, im->im_name) != 0)
    break;
    /* Note: here we store the NUL terminator too */
    - len = sprintf(id_str, "%d", im->im_id) + 1;
    + len = 1 + nfs_map_numeric_to_string(im->im_id, id_str,
    + sizeof(id_str));
    ret = nfs_idmap_instantiate(key, authkey, id_str, len);
    break;
    case IDMAP_CONV_IDTONAME:

    \
     
     \ /
      Last update: 2018-07-01 18:24    [W:4.035 / U:0.040 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site