4.12-stable review patch. If anyone has any objections, please let me know.
------------------ From: Martin Schwidefsky <[email protected]> commit 8ab867cb0806a8e195de161fd8883a0578d1d050 upstream. A 31-bit compat process can force a BUG_ON in crst_table_upgrade with specific, invalid mmap calls, e.g. mmap((void*) 0x7fff8000, 0x10000, 3, 32, -1, 0) The arch_get_unmapped_area[_topdown] functions miss an if condition in the decision to do a page table upgrade. [ms: Backport to 4.12, minor context change] Fixes: 9b11c7912d00 ("s390/mm: simplify arch_get_unmapped_area[_topdown]") Signed-off-by: Martin Schwidefsky <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/s390/mm/mmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/arch/s390/mm/mmap.c +++ b/arch/s390/mm/mmap.c @@ -119,7 +119,8 @@ arch_get_unmapped_area(struct file *filp return addr; check_asce_limit: - if (addr + len > current->mm->context.asce_limit) { + if (addr + len > current->mm->context.asce_limit && + addr + len <= TASK_SIZE) { rc = crst_table_upgrade(mm); if (rc) return (unsigned long) rc; @@ -183,7 +184,8 @@ arch_get_unmapped_area_topdown(struct fi } check_asce_limit: - if (addr + len > current->mm->context.asce_limit) { + if (addr + len > current->mm->context.asce_limit && + addr + len <= TASK_SIZE) { rc = crst_table_upgrade(mm); if (rc) return (unsigned long) rc;
