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    Subject[ 11/85] SUNRPC: Prevent kernel stack corruption on long values of flush
    Date
    3.6-stable review patch.  If anyone has any objections, please let me know.

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

    From: Sasha Levin <levinsasha928@gmail.com>

    commit 212ba90696ab4884e2025b0b13726d67aadc2cd4 upstream.

    The buffer size in read_flush() is too small for the longest possible values
    for it. This can lead to a kernel stack corruption:

    [ 43.047329] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff833e64b4
    [ 43.047329]
    [ 43.049030] Pid: 6015, comm: trinity-child18 Tainted: G W 3.5.0-rc7-next-20120716-sasha #221
    [ 43.050038] Call Trace:
    [ 43.050435] [<ffffffff836c60c2>] panic+0xcd/0x1f4
    [ 43.050931] [<ffffffff833e64b4>] ? read_flush.isra.7+0xe4/0x100
    [ 43.051602] [<ffffffff810e94e6>] __stack_chk_fail+0x16/0x20
    [ 43.052206] [<ffffffff833e64b4>] read_flush.isra.7+0xe4/0x100
    [ 43.052951] [<ffffffff833e6500>] ? read_flush_pipefs+0x30/0x30
    [ 43.053594] [<ffffffff833e652c>] read_flush_procfs+0x2c/0x30
    [ 43.053596] [<ffffffff812b9a8c>] proc_reg_read+0x9c/0xd0
    [ 43.053596] [<ffffffff812b99f0>] ? proc_reg_write+0xd0/0xd0
    [ 43.053596] [<ffffffff81250d5b>] do_loop_readv_writev+0x4b/0x90
    [ 43.053596] [<ffffffff81250fd6>] do_readv_writev+0xf6/0x1d0
    [ 43.053596] [<ffffffff812510ee>] vfs_readv+0x3e/0x60
    [ 43.053596] [<ffffffff812511b8>] sys_readv+0x48/0xb0
    [ 43.053596] [<ffffffff8378167d>] system_call_fastpath+0x1a/0x1f

    Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    net/sunrpc/cache.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/net/sunrpc/cache.c
    +++ b/net/sunrpc/cache.c
    @@ -1409,11 +1409,11 @@ static ssize_t read_flush(struct file *f
    size_t count, loff_t *ppos,
    struct cache_detail *cd)
    {
    - char tbuf[20];
    + char tbuf[22];
    unsigned long p = *ppos;
    size_t len;

    - sprintf(tbuf, "%lu\n", convert_to_wallclock(cd->flush_time));
    + snprintf(tbuf, sizeof(tbuf), "%lu\n", convert_to_wallclock(cd->flush_time));
    len = strlen(tbuf);
    if (p >= len)
    return 0;



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