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    Subject[34-longterm 144/179] proc: restrict access to /proc/PID/io
    Date
    From: Vasiliy Kulikov <segoon@openwall.com>

    -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
    -------------------

    commit 1d1221f375c94ef961ba8574ac4f85c8870ddd51 upstream.

    /proc/PID/io may be used for gathering private information. E.g. for
    openssh and vsftpd daemons wchars/rchars may be used to learn the
    precise password length. Restrict it to processes being able to ptrace
    the target process.

    ptrace_may_access() is needed to prevent keeping open file descriptor of
    "io" file, executing setuid binary and gathering io information of the
    setuid'ed process.

    Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
    ---
    fs/proc/base.c | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    diff --git a/fs/proc/base.c b/fs/proc/base.c
    index 268f00d..08741b0 100644
    --- a/fs/proc/base.c
    +++ b/fs/proc/base.c
    @@ -2518,6 +2518,9 @@ static int do_io_accounting(struct task_struct *task, char *buffer, int whole)
    struct task_io_accounting acct = task->ioac;
    unsigned long flags;

    + if (!ptrace_may_access(task, PTRACE_MODE_READ))
    + return -EACCES;
    +
    if (whole && lock_task_sighand(task, &flags)) {
    struct task_struct *t = task;

    @@ -2640,7 +2643,7 @@ static const struct pid_entry tgid_base_stuff[] = {
    REG("coredump_filter", S_IRUGO|S_IWUSR, proc_coredump_filter_operations),
    #endif
    #ifdef CONFIG_TASK_IO_ACCOUNTING
    - INF("io", S_IRUGO, proc_tgid_io_accounting),
    + INF("io", S_IRUSR, proc_tgid_io_accounting),
    #endif
    };

    @@ -2976,7 +2979,7 @@ static const struct pid_entry tid_base_stuff[] = {
    REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
    #endif
    #ifdef CONFIG_TASK_IO_ACCOUNTING
    - INF("io", S_IRUGO, proc_tid_io_accounting),
    + INF("io", S_IRUSR, proc_tid_io_accounting),
    #endif
    };

    --
    1.7.9.6


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