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    Subject[PATCH v2 0/5] Reenable might_sleep() checks for might_fault()
    Date
    v1 -> v2:
    - moved pagefault_count to the end of thread_info for all archs that would have
    required manually calculating asm-offsets - to keep changes minimal.
    - remove unlikely() from "mm, uaccess: trigger might_sleep() in" and keep
    changes minimal (in_atomic() -> pagefault_disabled())

    ----

    I recently discovered that might_fault() doesn't call might_sleep() anymore.
    Therefore bugs like:
    spin_lock(&lock);
    rc = copy_to_user(...);
    spin_unlock(&lock);
    would not be detected with CONFIG_DEBUG_ATOMIC_SLEEP. The code was changed to
    disable false positives for code like:
    pagefault_disable();
    rc = copy_to_user(...);
    pagefault_enable();

    Until now, pagefault_disable() and pagefault_enable() simply modified the
    preempt count, therefore telling the pagefault handler that the context is
    atomic and sleeping is disallowed.

    In order to reenable might_sleep() checks for the correct path, we need a way to
    detect whether we run in a pagefault_disable() context.

    This series therefore introduces a separate pagefault_count and uses it to count
    the levels of pagefault_disable() per thread. might_sleep() checks are
    reactivated for the !pagefault_disable() path.

    So this should now work:
    spin_lock(&lock); /* also if left away */
    pagefault_disable()
    rc = copy_to_user(...);
    pagefault_enable();
    spin_unlock(&lock);
    And this should report a warning again:
    spin_lock(&lock);
    rc = copy_to_user(...);
    spin_unlock(&lock);

    Please note that this series will not completely split the handling of
    pagefault_disable() and the preempt count. This will be done in another series.
    Purpose of this series is to reenable might_sleep() checks for might_fault(),
    avoiding to produce false positives.

    Cross compiled on powerpc, arm, sparc, sparc64, arm64, x86_64, i386, mips,
    alpha, ia64, xtensa, m68k, microblaze.

    Tested on s390.


    David Hildenbrand (5):
    uaccess: add pagefault_count to thread_info
    uaccess: count pagefault_disable() levels in pagefault_count
    mm, uaccess: trigger might_sleep() in might_fault() when pagefaults
    are disabled
    uaccess: clarify that uaccess may only sleep if pagefaults are not
    disabled
    uaccess: CONFIG_DEBUG_PAGEFAULT_COUNT to debug pagefault_count

    arch/alpha/include/asm/thread_info.h | 1 +
    arch/arc/include/asm/thread_info.h | 1 +
    arch/arm/include/asm/thread_info.h | 1 +
    arch/arm64/include/asm/thread_info.h | 1 +
    arch/avr32/include/asm/thread_info.h | 1 +
    arch/avr32/include/asm/uaccess.h | 12 +++++---
    arch/blackfin/include/asm/thread_info.h | 1 +
    arch/c6x/include/asm/thread_info.h | 1 +
    arch/cris/include/asm/thread_info.h | 1 +
    arch/frv/include/asm/thread_info.h | 1 +
    arch/hexagon/include/asm/thread_info.h | 1 +
    arch/hexagon/include/asm/uaccess.h | 3 +-
    arch/ia64/include/asm/thread_info.h | 1 +
    arch/m32r/include/asm/thread_info.h | 1 +
    arch/m32r/include/asm/uaccess.h | 30 ++++++++++++------
    arch/m68k/include/asm/thread_info.h | 1 +
    arch/metag/include/asm/thread_info.h | 1 +
    arch/microblaze/include/asm/thread_info.h | 1 +
    arch/microblaze/include/asm/uaccess.h | 6 ++--
    arch/mips/include/asm/thread_info.h | 1 +
    arch/mips/include/asm/uaccess.h | 45 ++++++++++++++++++---------
    arch/mn10300/include/asm/thread_info.h | 1 +
    arch/openrisc/include/asm/thread_info.h | 1 +
    arch/parisc/include/asm/thread_info.h | 1 +
    arch/powerpc/include/asm/thread_info.h | 1 +
    arch/s390/include/asm/thread_info.h | 1 +
    arch/s390/include/asm/uaccess.h | 15 ++++++---
    arch/score/include/asm/thread_info.h | 1 +
    arch/score/include/asm/uaccess.h | 15 ++++++---
    arch/sh/include/asm/thread_info.h | 1 +
    arch/sparc/include/asm/thread_info_32.h | 1 +
    arch/sparc/include/asm/thread_info_64.h | 1 +
    arch/tile/include/asm/thread_info.h | 1 +
    arch/tile/include/asm/uaccess.h | 21 ++++++++-----
    arch/um/include/asm/thread_info.h | 1 +
    arch/unicore32/include/asm/thread_info.h | 1 +
    arch/x86/include/asm/thread_info.h | 1 +
    arch/x86/include/asm/uaccess.h | 15 ++++++---
    arch/x86/include/asm/uaccess_32.h | 6 ++--
    arch/x86/lib/usercopy_32.c | 6 ++--
    arch/xtensa/include/asm/thread_info.h | 1 +
    include/linux/kernel.h | 3 +-
    include/linux/uaccess.h | 51 ++++++++++++++++++++++++++-----
    lib/Kconfig.debug | 9 ++++++
    lib/strnlen_user.c | 6 ++--
    mm/maccess.c | 11 +++++++
    mm/memory.c | 18 ++++-------
    47 files changed, 222 insertions(+), 80 deletions(-)

    --
    1.8.5.5



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