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Commit 8ab867cb authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390/mm: fix BUG_ON in crst_table_upgrade 



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.

Fixes: 9b11c791 ("s390/mm: simplify arch_get_unmapped_area[_topdown]")
Cc: <stable@vger.kernel.org>  # v4.12+
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 0b89ede6

arch/s390/mm/mmap.c

+4 −2
Original line number Diff line number Diff line
@@ -119,7 +119,8 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, 
		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, addr + len);

		if (rc)

			return (unsigned long) rc;
@@ -183,7 +184,8 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, 
	}



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, addr + len);

		if (rc)

			return (unsigned long) rc;