On Tue, Jul 09, 2024 at 04:21:22AM -0500, Donet Tom wrote:
> 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.
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!
> #
>
> V2:
> Added vm_end_gap() check.
>
> V1:
> https://lore.kernel.org/all/20240705071150.84972-1-donettom@xxxxxxxxxxxxx/
>
> Reported-by Pavithra Prakash <pavrampu@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Donet Tom <donettom@xxxxxxxxxxxxx>
Please use "hugetlbfs:" as subject prefix. No need to spell out full path.
Otherwise,
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
--
Kiryl Shutsemau / Kirill A. Shutemov
