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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2017-12-15 14:16:04 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2017-12-15 15:05:21 +0100
commit9f37e797547cca9d14fe1f0f43f5c89b261ff0b0 (patch)
treecce20db0086ff4aeb345991c44ddcb15588a412b /arch/s390/lib
parent366d8216488319ed29308b977cd62b7964a779b7 (diff)
s390: fix preemption race in disable_sacf_uaccess
With CONFIG_PREEMPT=y there is a possible race in disable_sacf_uaccess. The new set_fs value needs to be stored the the task structure first, the control register update needs to be second. Otherwise a preemptive schedule may interrupt the code right after the control register update has been done and the next time the task is scheduled we get an incorrect value in the control register due to the old set_fs setting. Fixes: 0aaba41b58 ("s390: remove all code using the access register mode") Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/lib')
-rw-r--r--arch/s390/lib/uaccess.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/s390/lib/uaccess.c b/arch/s390/lib/uaccess.c
index cae5a1e16cbd..c4f8039a35e8 100644
--- a/arch/s390/lib/uaccess.c
+++ b/arch/s390/lib/uaccess.c
@@ -89,11 +89,11 @@ EXPORT_SYMBOL(enable_sacf_uaccess);
void disable_sacf_uaccess(mm_segment_t old_fs)
{
+ current->thread.mm_segment = old_fs;
if (old_fs == USER_DS && test_facility(27)) {
__ctl_load(S390_lowcore.user_asce, 1, 1);
clear_cpu_flag(CIF_ASCE_PRIMARY);
}
- current->thread.mm_segment = old_fs;
}
EXPORT_SYMBOL(disable_sacf_uaccess);

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