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author | Vincent Whitchurch <vincent.whitchurch@axis.com> | 2018-11-09 10:12:30 +0100 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-12-21 10:40:52 +0100 |
commit | fd9beff0ccd0ef44078be23d6ce5ba431e23f292 (patch) | |
tree | cef92260b7a6303196aa88e3e9ce08625c769884 /drivers | |
parent | f443ac6116d640e4f9f39692e667c64bad3ee549 (diff) |
ARM: 8813/1: Make aligned 2-byte getuser()/putuser() atomic on ARMv6+
[ Upstream commit 344eb5539abf3e0b6ce22568c03e86450073e097 ]
getuser() and putuser() (and there underscored variants) use two
strb[t]/ldrb[t] instructions when they are asked to get/put 16-bits.
This means that the read/write is not atomic even when performed to a
16-bit-aligned address.
This leads to problems with vhost: vhost uses __getuser() to read the
vring's 16-bit avail.index field, and if it happens to observe a partial
update of the index, wrong descriptors will be used which will lead to a
breakdown of the virtio communication. A similar problem exists for
__putuser() which is used to write to the vring's used.index field.
The reason these functions use strb[t]/ldrb[t] is because strht/ldrht
instructions did not exist until ARMv6T2/ARMv7. So we should be easily
able to fix this on ARMv7. Also, since all ARMv6 processors also don't
actually use the unprivileged instructions anymore for uaccess (since
CONFIG_CPU_USE_DOMAINS is not used) we can easily fix them too.
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers')
0 files changed, 0 insertions, 0 deletions