[PATCH v3 0/4] uaccess: Add unsafe accessors for arm64

Julien Thierry
2019-01-15T13:58:40Z

Hi,

First version of this series[1] was briefly in linux-next but had to be
reverted due to a bug where schedule would end up being called while
user_access was active[2].

After clarifications[3], rescheduling while in a user_access region is not
allowed.

* Patches 1 and 2 implement the unsafe accessors for arm64
* Patches 3 and 4 clarify this restriction in the API and attempts to
check against violations of the restriction.

Changes since v2[4]:
- Rebase on v5.0-rc2
- access_ok() is now done in user_access_begin(), so rework accessors
so access_ok() is not called in unsafe_get/put_user()
- Split addition of unsafe accessors and the user_access_region check
into separate patches
- Avoid reading SCTLR_EL1 in user_access_region check
- Add build option for user_access_region checking
- Reword clarifications on unsafe accessors API

Changes since v1[1]:
- Add a way to detect code calling schedule within a user_access region
- Make sure put_user/get_user arguments are evaluated before disabling PAN

[1] https://www.spinics.net/lists/arm-kernel/msg674925.html
[2] https://patchwork.kernel.org/patch/10634783/
[3] https://lkml.org/lkml/2018/11/28/50
[4] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-December/617080.html

Cheers,

Julien

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Julien Thierry (4):
arm64: uaccess: Cleanup get/put_user()
arm64: uaccess: Implement unsafe accessors
uaccess: Check no rescheduling function is called in unsafe region
arm64: uaccess: Implement user_access_region_active

arch/arm64/include/asm/sysreg.h | 2 +
arch/arm64/include/asm/uaccess.h | 123 ++++++++++++++++++++++++++-------------
include/linux/kernel.h | 11 +++-
include/linux/uaccess.h | 13 +++++
kernel/sched/core.c | 22 +++++++
lib/Kconfig.debug | 8 +++
6 files changed, 135 insertions(+), 44 deletions(-)

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