From: Benjamin Berg <benjamin.b...@intel.com>
We may have a TASK_SIZE from the host that is bigger than UML is able to
address with a three-level pagetable. Guard against that by clipping the
maximum TASK_SIZE to the maximum addressable area.
Signed-off-by: Benjamin Berg <benjamin.b...@intel.com>
---
v7: Fix integer overflow on 32 bit with 3-level page tables
---
arch/um/kernel/um_arch.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 25cd2c6d7e95..f82dd4e854f3 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -334,11 +334,16 @@ int __init linux_main(int argc, char **argv)
stub_start -= PAGE_SIZE;
host_task_size = stub_start;
+ /* Limit TASK_SIZE to what is addressable by the page table */
+ task_size = host_task_size;
+ if (task_size > (unsigned long long) PTRS_PER_PGD * PGDIR_SIZE)
+ task_size = PTRS_PER_PGD * PGDIR_SIZE;
+
/*
* TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps
* out
*/
- task_size = host_task_size & PGDIR_MASK;
+ task_size = task_size & PGDIR_MASK;
/* OS sanity checks that need to happen before the kernel runs */
os_early_checks();
--
2.45.2
