dffe24e958
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 maintain
stack gap.
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!
#
Link: https://lkml.kernel.org/r/20240710051912.4681-1-donettom@linux.ibm.com
Signed-off-by: Donet Tom <donettom@linux.ibm.com>
Reported-by Pavithra Prakash <pavrampu@linux.vnet.ibm.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Tony Battersby <tonyb@cybernetics.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.