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    Subject[PATCH 3.16.y-ckt 239/254] perf: Handle compat ioctl
    Date
    3.16.7-ckt2 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Pawel Moll <pawel.moll@arm.com>

    commit b3f207855f57b9c8f43a547a801340bb5cbc59e5 upstream.

    When running a 32-bit userspace on a 64-bit kernel (eg. i386
    application on x86_64 kernel or 32-bit arm userspace on arm64
    kernel) some of the perf ioctls must be treated with special
    care, as they have a pointer size encoded in the command.

    For example, PERF_EVENT_IOC_ID in 32-bit world will be encoded
    as 0x80042407, but 64-bit kernel will expect 0x80082407. In
    result the ioctl will fail returning -ENOTTY.

    This patch solves the problem by adding code fixing up the
    size as compat_ioctl file operation.

    Reported-by: Drew Richardson <drew.richardson@arm.com>
    Signed-off-by: Pawel Moll <pawel.moll@arm.com>
    Signed-off-by: Peter Zijlstra <peterz@infradead.org>
    Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Link: http://lkml.kernel.org/r/1402671812-9078-1-git-send-email-pawel.moll@arm.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    kernel/events/core.c | 23 ++++++++++++++++++++++-
    1 file changed, 22 insertions(+), 1 deletion(-)

    diff --git a/kernel/events/core.c b/kernel/events/core.c
    index 5dfa199971d2..6bc75223aaa7 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -41,6 +41,7 @@
    #include <linux/cgroup.h>
    #include <linux/module.h>
    #include <linux/mman.h>
    +#include <linux/compat.h>

    #include "internal.h"

    @@ -3747,6 +3748,26 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
    return 0;
    }

    +#ifdef CONFIG_COMPAT
    +static long perf_compat_ioctl(struct file *file, unsigned int cmd,
    + unsigned long arg)
    +{
    + switch (_IOC_NR(cmd)) {
    + case _IOC_NR(PERF_EVENT_IOC_SET_FILTER):
    + case _IOC_NR(PERF_EVENT_IOC_ID):
    + /* Fix up pointer size (usually 4 -> 8 in 32-on-64-bit case */
    + if (_IOC_SIZE(cmd) == sizeof(compat_uptr_t)) {
    + cmd &= ~IOCSIZE_MASK;
    + cmd |= sizeof(void *) << IOCSIZE_SHIFT;
    + }
    + break;
    + }
    + return perf_ioctl(file, cmd, arg);
    +}
    +#else
    +# define perf_compat_ioctl NULL
    +#endif
    +
    int perf_event_task_enable(void)
    {
    struct perf_event *event;
    @@ -4252,7 +4273,7 @@ static const struct file_operations perf_fops = {
    .read = perf_read,
    .poll = perf_poll,
    .unlocked_ioctl = perf_ioctl,
    - .compat_ioctl = perf_ioctl,
    + .compat_ioctl = perf_compat_ioctl,
    .mmap = perf_mmap,
    .fasync = perf_fasync,
    };
    --
    2.1.0


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