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    Subject[ 34/48] kernel/kmod.c: check for NULL in call_usermodehelper_exec()
    Date
    3.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

    commit 4c1c7be95c345cf2ad537a0c48e9aeadc7304527 upstream.

    If /proc/sys/kernel/core_pattern contains only "|", a NULL pointer
    dereference happens upon core dump because argv_split("") returns
    argv[0] == NULL.

    This bug was once fixed by commit 264b83c07a84 ("usermodehelper: check
    subprocess_info->path != NULL") but was by error reintroduced by commit
    7f57cfa4e2aa ("usermodehelper: kill the sub_info->path[0] check").

    This bug seems to exist since 2.6.19 (the version which core dump to
    pipe was added). Depending on kernel version and config, some side
    effect might happen immediately after this oops (e.g. kernel panic with
    2.6.32-358.18.1.el6).

    Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Acked-by: Oleg Nesterov <oleg@redhat.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/kmod.c | 4 ++++
    1 file changed, 4 insertions(+)

    --- a/kernel/kmod.c
    +++ b/kernel/kmod.c
    @@ -540,6 +540,10 @@ int call_usermodehelper_exec(struct subp
    DECLARE_COMPLETION_ONSTACK(done);
    int retval = 0;

    + if (!sub_info->path) {
    + call_usermodehelper_freeinfo(sub_info);
    + return -EINVAL;
    + }
    helper_lock();
    if (!sub_info->path) {
    retval = -EINVAL;



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