From: Vasily Gorbik gor@linux.ibm.com
[ Upstream commit 190f056fba230abee80712eb810939ef9a8c462f ]
While "s390/vdso: avoid 64-bit vdso mapping for compat tasks" fixed 64-bit vdso mapping for compat tasks under gdb it introduced another problem. "compat_mm" flag is not inherited during fork and when 31-bit process forks a child (but does not perform exec) it ends up with 64-bit vdso. To address that, init_new_context (which is called during fork and exec) now initialize compat_mm based on thread TIF_31BIT flag. Later compat_mm is adjusted in arch_setup_additional_pages, which is called during exec.
Fixes: d1befa65823e ("s390/vdso: avoid 64-bit vdso mapping for compat tasks") Reported-by: Stefan Liebler stli@linux.ibm.com Reviewed-by: Heiko Carstens heiko.carstens@de.ibm.com Cc: stable@vger.kernel.org # v4.20+ Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/include/asm/mmu_context.h | 2 +- arch/s390/kernel/vdso.c | 5 ++--- 2 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h index e4462202200d7..8d04e6f3f7964 100644 --- a/arch/s390/include/asm/mmu_context.h +++ b/arch/s390/include/asm/mmu_context.h @@ -25,7 +25,7 @@ static inline int init_new_context(struct task_struct *tsk, atomic_set(&mm->context.flush_count, 0); mm->context.gmap_asce = 0; mm->context.flush_mm = 0; - mm->context.compat_mm = 0; + mm->context.compat_mm = test_thread_flag(TIF_31BIT); #ifdef CONFIG_PGSTE mm->context.alloc_pgste = page_table_allocate_pgste || test_thread_flag(TIF_PGSTE) || diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c index ec31b48a42a52..7ab7d256d1eb7 100644 --- a/arch/s390/kernel/vdso.c +++ b/arch/s390/kernel/vdso.c @@ -224,10 +224,9 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
vdso_pages = vdso64_pages; #ifdef CONFIG_COMPAT - if (is_compat_task()) { + mm->context.compat_mm = is_compat_task(); + if (mm->context.compat_mm) vdso_pages = vdso32_pages; - mm->context.compat_mm = 1; - } #endif /* * vDSO has a problem and was disabled, just don't "enable" it for