[RFC 4/6] mm: swap: Add randomization check for swapon/off calls
From: Vivek Kumar <hidden>
Date: 2022-05-18 07:49:45
Also in:
linux-arm-kernel, linux-doc, linux-mm, linux-pm, lkml
Subsystem:
memory management, memory management - swap, the rest · Maintainers:
Andrew Morton, Chris Li, Kairui Song, Linus Torvalds
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 <redacted> Signed-off-by: Prasanna Kumar <redacted> --- 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