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authorDaniel Black <daniel@linux.ibm.com>2018-10-05 15:52:19 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-10-05 16:32:05 -0700
commitd41aa5252394c065d1f04d1ceea885b70d00c9c6 (patch)
tree11a061a0a323119758ea3266449b2fc499705a83
parentcbe355f57c8074bc4f452e5b6e35509044c6fa23 (diff)
downloadlinux-stericsson-d41aa5252394c065d1f04d1ceea885b70d00c9c6.tar.gz
mm: madvise(MADV_DODUMP): allow hugetlbfs pages
Reproducer, assuming 2M of hugetlbfs available: Hugetlbfs mounted, size=2M and option user=testuser # mount | grep ^hugetlbfs hugetlbfs on /dev/hugepages type hugetlbfs (rw,pagesize=2M,user=dan) # sysctl vm.nr_hugepages=1 vm.nr_hugepages = 1 # grep Huge /proc/meminfo AnonHugePages: 0 kB ShmemHugePages: 0 kB HugePages_Total: 1 HugePages_Free: 1 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Hugetlb: 2048 kB Code: #include <sys/mman.h> #include <stddef.h> #define SIZE 2*1024*1024 int main() { void *ptr; ptr = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_HUGETLB | MAP_ANONYMOUS, -1, 0); madvise(ptr, SIZE, MADV_DONTDUMP); madvise(ptr, SIZE, MADV_DODUMP); } Compile and strace: mmap(NULL, 2097152, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_HUGETLB, -1, 0) = 0x7ff7c9200000 madvise(0x7ff7c9200000, 2097152, MADV_DONTDUMP) = 0 madvise(0x7ff7c9200000, 2097152, MADV_DODUMP) = -1 EINVAL (Invalid argument) hugetlbfs pages have VM_DONTEXPAND in the VmFlags driver pages based on author testing with analysis from Florian Weimer[1]. The inclusion of VM_DONTEXPAND into the VM_SPECIAL defination was a consequence of the large useage of VM_DONTEXPAND in device drivers. A consequence of [2] is that VM_DONTEXPAND marked pages are unable to be marked DODUMP. A user could quite legitimately madvise(MADV_DONTDUMP) their hugetlbfs memory for a while and later request that madvise(MADV_DODUMP) on the same memory. We correct this omission by allowing madvice(MADV_DODUMP) on hugetlbfs pages. [1] https://stackoverflow.com/questions/52548260/madvisedodump-on-the-same-ptr-size-as-a-successful-madvisedontdump-fails-wit [2] commit 0103bd16fb90 ("mm: prepare VM_DONTDUMP for using in drivers") Link: http://lkml.kernel.org/r/20180930054629.29150-1-daniel@linux.ibm.com Link: https://lists.launchpad.net/maria-discuss/msg05245.html Fixes: 0103bd16fb90 ("mm: prepare VM_DONTDUMP for using in drivers") Reported-by: Kenneth Penza <kpenza@gmail.com> Signed-off-by: Daniel Black <daniel@linux.ibm.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Konstantin Khlebnikov <khlebnikov@openvz.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--mm/madvise.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/madvise.c b/mm/madvise.c
index 972a9eaa898b..71d21df2a3f3 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -96,7 +96,7 @@ static long madvise_behavior(struct vm_area_struct *vma,
new_flags |= VM_DONTDUMP;
break;
case MADV_DODUMP:
- if (new_flags & VM_SPECIAL) {
+ if (!is_vm_hugetlb_page(vma) && new_flags & VM_SPECIAL) {
error = -EINVAL;
goto out;
}