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Message-ID: <20240709092122.41232-1-donettom@linux.ibm.com>
Date: Tue, 9 Jul 2024 04:21:22 -0500
From: Donet Tom <donettom@...ux.ibm.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Muchun Song <muchun.song@...ux.dev>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Ritesh Harjani <ritesh.list@...il.com>,
Mike Rapoport <rppt@...nel.org>, David Hildenbrand <david@...hat.com>,
Matthew Wilcox <willy@...radead.org>,
Tony Battersby <tonyb@...ernetics.com>,
"Aneesh Kumar K . V" <aneesh.kumar@...nel.org>,
Nicholas Piggin <npiggin@...il.com>,
Alexei Starovoitov <ast@...nel.org>, Andy Lutomirski <luto@...nel.org>,
Donet Tom <donettom@...ux.ibm.com>
Subject: [PATCH v2] fs/hugetlbfs/inode.c: Ensure generic_hugetlb_get_unmapped_area() returns higher address than mmap_min_addr
generic_hugetlb_get_unmapped_area() was returning an address less
than mmap_min_addr if the mmap argument addr, after alignment, was
less than mmap_min_addr, causing mmap to fail.
This is because current generic_hugetlb_get_unmapped_area() code does
not take into account mmap_min_addr.
This patch ensures that generic_hugetlb_get_unmapped_area() always returns
an address that is greater than mmap_min_addr. Additionally, similar to
generic_get_unmapped_area(), vm_end_gap() checks are included to ensure
that the address is within the limit.
How to reproduce
================
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <unistd.h>
#define HUGEPAGE_SIZE (16 * 1024 * 1024)
int main() {
void *addr = mmap((void *)-1, HUGEPAGE_SIZE,
PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);
if (addr == MAP_FAILED) {
perror("mmap");
exit(EXIT_FAILURE);
}
snprintf((char *)addr, HUGEPAGE_SIZE, "Hello, Huge Pages!");
printf("%s\n", (char *)addr);
if (munmap(addr, HUGEPAGE_SIZE) == -1) {
perror("munmap");
exit(EXIT_FAILURE);
}
return 0;
}
Result without fix
==================
# cat /proc/meminfo |grep -i HugePages_Free
HugePages_Free: 20
# ./test
mmap: Permission denied
#
Result with fix
===============
# cat /proc/meminfo |grep -i HugePages_Free
HugePages_Free: 20
# ./test
Hello, Huge Pages!
#
V2:
Added vm_end_gap() check.
V1:
https://lore.kernel.org/all/20240705071150.84972-1-donettom@linux.ibm.com/
Reported-by Pavithra Prakash <pavrampu@...ux.vnet.ibm.com>
Signed-off-by: Donet Tom <donettom@...ux.ibm.com>
---
fs/hugetlbfs/inode.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 412f295acebe..cdd8e53ddd19 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -222,13 +222,13 @@ generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
unsigned long flags)
{
struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma;
+ struct vm_area_struct *vma, *prev;
struct hstate *h = hstate_file(file);
const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags);
if (len & ~huge_page_mask(h))
return -EINVAL;
- if (len > TASK_SIZE)
+ if (len > mmap_end - mmap_min_addr)
return -ENOMEM;
if (flags & MAP_FIXED) {
@@ -239,9 +239,10 @@ generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
if (addr) {
addr = ALIGN(addr, huge_page_size(h));
- vma = find_vma(mm, addr);
- if (mmap_end - len >= addr &&
- (!vma || addr + len <= vm_start_gap(vma)))
+ vma = find_vma_prev(mm, addr, &prev);
+ if (mmap_end - len >= addr && addr >= mmap_min_addr &&
+ (!vma || addr + len <= vm_start_gap(vma)) &&
+ (!prev || addr >= vm_end_gap(prev)))
return addr;
}
--
2.43.5
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