[RFC 4/6] mm: swap: Add randomization check for swapon/off calls

Vivek Kumar
2022-05-18T07:49:43Z

Add addtional check on swapon/swapoff sycalls to disable
randomization of swap offsets if GENHD_FL_NO_RANDOMIZE
flag is passed.

Signed-off-by: Vivek Kumar <quic_vivekuma@quicinc.com>
Signed-off-by: Prasanna Kumar <quic_kprasan@quicinc.com>
---
mm/swapfile.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 1c3d5b9..a3eeab6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2474,7 +2474,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
if (p->flags & SWP_CONTINUED)
free_swap_count_continuations(p);

- if (!p->bdev || !bdev_nonrot(p->bdev))
+ if (!p->bdev || (p->bdev->bd_disk->flags & GENHD_FL_NO_RANDOMIZE)
+ || !bdev_nonrot(p->bdev))
atomic_dec(&nr_rotate_swap);

mutex_lock(&swapon_mutex);
@@ -3065,7 +3066,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
if (p->bdev && p->bdev->bd_disk->fops->rw_page)
p->flags |= SWP_SYNCHRONOUS_IO;

- if (p->bdev && bdev_nonrot(p->bdev)) {
+ if (p->bdev && !(p->bdev->bd_disk->flags & GENHD_FL_NO_RANDOMIZE) &&
+ bdev_nonrot(p->bdev)) {
int cpu;
unsigned long ci, nr_cluster;

--
2.7.4