Hi
The patch 8d7071af8907 ("mm: always expand the stack with the mmap write
lock held") breaks PA-RISC.
The breakage happens if we attempt to pass more arguments to execve than
what fits into the initial stack page - we get -E2BIG in such a case.
The reason for the breakage is that the commit 8d7071af8907 adds the test
"if (!(vma->vm_flags & VM_GROWSDOWN)) return -EFAULT;" to the function
expand_downwards.
expand_downwards is called from get_arg_page to allocate initial stack
pages. With the added test for VM_GROWSDOWN, it is not able to allocate
any pages on PA-RISC at all, and execve fails as soon as it tries to
allocate a stack page.
The bug can be fixed by dropping the test for VM_GROWSDOWN from
expand_downwards.
Fixes: 8d7071af8907 ("mm: always expand the stack with the mmap write lock held")
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v6.4
---
mm/mmap.c | 3 ---
1 file changed, 3 deletions(-)
Index: linux-6.4.1/mm/mmap.c
===================================================================
--- linux-6.4.1.orig/mm/mmap.c 2023-07-03 18:17:35.000000000 +0200
+++ linux-6.4.1/mm/mmap.c 2023-07-03 21:22:44.000000000 +0200
@@ -2036,9 +2036,6 @@ int expand_downwards(struct vm_area_stru
struct vm_area_struct *prev;
int error = 0;
- if (!(vma->vm_flags & VM_GROWSDOWN))
- return -EFAULT;
-
address &= PAGE_MASK;
if (address < mmap_min_addr || address < FIRST_USER_ADDRESS)
return -EPERM;
