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    Subject[PATCH 3/3] execve: make responsive to SIGKILL with large arguments
    Date
    An execve with a very large total of argument/environment strings
    can take a really long time in the execve system call. It runs
    uninterruptibly to count and copy all the strings. This change
    makes it abort the exec quickly if sent a SIGKILL.

    Note that this is the conservative change, to interrupt only for
    SIGKILL, by using fatal_signal_pending(). It would be perfectly
    correct semantics to let any signal interrupt the string-copying in
    execve, i.e. use signal_pending() instead of fatal_signal_pending().
    We'll save that change for later, since it could have user-visible
    consequences, such as having a timer set too quickly make it so that
    an execve can never complete, though it always happened to work before.

    Signed-off-by: Roland McGrath <roland@redhat.com>
    ---
    fs/exec.c | 7 +++++++
    1 files changed, 7 insertions(+), 0 deletions(-)

    diff --git a/fs/exec.c b/fs/exec.c
    index 6f2d777..828dd24 100644
    --- a/fs/exec.c
    +++ b/fs/exec.c
    @@ -376,6 +376,9 @@ static int count(const char __user * const __user * argv, int max)
    argv++;
    if (i++ >= max)
    return -E2BIG;
    +
    + if (fatal_signal_pending(current))
    + return -ERESTARTNOHAND;
    cond_resched();
    }
    }
    @@ -419,6 +422,10 @@ static int copy_strings(int argc, const char __user *const __user *argv,
    while (len > 0) {
    int offset, bytes_to_copy;

    + if (fatal_signal_pending(current)) {
    + ret = -ERESTARTNOHAND;
    + goto out;
    + }
    cond_resched();

    offset = pos % PAGE_SIZE;

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