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s390/mm: fix BUG_ON in crst_table_upgrade

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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: 9b11c7912d ("s390/mm: simplify arch_get_unmapped_area[_topdown]")
Cc: <stable@vger.kernel.org>  # v4.12+
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2017-08-31 13:18:22 +02:00
parent 0b89ede629
commit 8ab867cb08
1 changed files with 4 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

6
arch/s390/mm/mmap.c
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@ -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;