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    SubjectRe: [PATCH 1/4] signals: SEND_SIG_NOINFO should be considered as SI_FROMUSER()
    Oleg Nesterov [oleg@redhat.com] wrote:
    | No changes in compiled code. The patch adds the new helper, si_fromuser()
    | and changes check_kill_permission() to use this helper.
    |
    | The real effect of this patch is that from now we "officially" consider
    | SEND_SIG_NOINFO signal as "from user-space" signals. This is already true
    | if we look at the code which uses SEND_SIG_NOINFO, except __send_signal()
    | has another opinion - see the next patch.
    |
    | The naming of these special SEND_SIG_XXX siginfo's is really bad imho.

    I agree :-)

    | >From __send_signal()'s pov they mean
    |
    | SEND_SIG_NOINFO from user

    Just to complicate further, all 'SEND_SIG_NOINFO' signals are from user,
    but not all 'from user' signals are SEND_SIG_NOINFO.

    | SEND_SIG_PRIV from kernel

    SEND_SIG_PRIV also means there is no real info, just that sender is
    privileged.

    | SEND_SIG_FORCED no info

    Are 'forced' signals considered 'from kernel' too ?

    Separate from this patch, but would be good if we could fix the naming.

    |
    | Signed-off-by: Oleg Nesterov <oleg@redhat.com>
    | ---
    |
    | include/linux/sched.h | 5 -----
    | kernel/signal.c | 16 +++++++++++++---
    | 2 files changed, 13 insertions(+), 8 deletions(-)
    |
    | --- TTT_32/include/linux/sched.h~FU_1_HELPER 2009-09-24 21:38:54.000000000 +0200
    | +++ TTT_32/include/linux/sched.h 2009-10-04 02:21:49.000000000 +0200
    | @@ -2081,11 +2081,6 @@ static inline int kill_cad_pid(int sig,
    | #define SEND_SIG_PRIV ((struct siginfo *) 1)
    | #define SEND_SIG_FORCED ((struct siginfo *) 2)
    |
    | -static inline int is_si_special(const struct siginfo *info)
    | -{
    | - return info <= SEND_SIG_FORCED;
    | -}
    | -
    | /* True if we are on the alternate signal stack. */
    |
    | static inline int on_sig_stack(unsigned long sp)
    | --- TTT_32/kernel/signal.c~FU_1_HELPER 2009-09-24 21:38:54.000000000 +0200
    | +++ TTT_32/kernel/signal.c 2009-10-04 02:21:55.000000000 +0200
    | @@ -584,6 +584,17 @@ static int rm_from_queue(unsigned long m
    | return 1;
    | }
    |
    | +static inline int is_si_special(const struct siginfo *info)
    | +{
    | + return info <= SEND_SIG_FORCED;
    | +}
    | +
    | +static inline bool si_fromuser(const struct siginfo *info)
    | +{
    | + return info == SEND_SIG_NOINFO ||
    | + (!is_si_special(info) && SI_FROMUSER(info));
    | +}
    | +

    This change makes sense, but can we even drop the SEND_SIG_NOINFO
    altogether and simply check for NULL:

    return (!info || (is_si_special(info)) && SI_FROMUSER(info))

    Sukadev


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