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authorGregory Price <gourry.memverge@gmail.com>2023-10-03 10:48:56 -0400
committerAndrew Morton <akpm@linux-foundation.org>2023-10-06 14:11:38 -0700
commit229e2253766c7cdfe024f1fe280020cc4711087c (patch)
tree504d51f51067d3c9832d4bf887f6b674c78485b4
parent1de195dd0e05d9cba43dec16f83d4ee32af94dd2 (diff)
mm/migrate: fix do_pages_move for compat pointers
do_pages_move does not handle compat pointers for the page list. correctly. Add in_compat_syscall check and appropriate get_user fetch when iterating the page list. It makes the syscall in compat mode (32-bit userspace, 64-bit kernel) work the same way as the native 32-bit syscall again, restoring the behavior before my broken commit 5b1b561ba73c ("mm: simplify compat_sys_move_pages"). More specifically, my patch moved the parsing of the 'pages' array from the main entry point into do_pages_stat(), which left the syscall working correctly for the 'stat' operation (nodes = NULL), while the 'move' operation (nodes != NULL) is now missing the conversion and interprets 'pages' as an array of 64-bit pointers instead of the intended 32-bit userspace pointers. It is possible that nobody noticed this bug because the few applications that actually call move_pages are unlikely to run in compat mode because of their large memory requirements, but this clearly fixes a user-visible regression and should have been caught by ltp. Link: https://lkml.kernel.org/r/20231003144857.752952-1-gregory.price@memverge.com Fixes: 5b1b561ba73c ("mm: simplify compat_sys_move_pages") Signed-off-by: Gregory Price <gregory.price@memverge.com> Reported-by: Arnd Bergmann <arnd@arndb.de> Co-developed-by: Arnd Bergmann <arnd@arndb.de> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--mm/migrate.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 2053b54556ca..06086dc9da28 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2162,6 +2162,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
const int __user *nodes,
int __user *status, int flags)
{
+ compat_uptr_t __user *compat_pages = (void __user *)pages;
int current_node = NUMA_NO_NODE;
LIST_HEAD(pagelist);
int start, i;
@@ -2174,8 +2175,17 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
int node;
err = -EFAULT;
- if (get_user(p, pages + i))
- goto out_flush;
+ if (in_compat_syscall()) {
+ compat_uptr_t cp;
+
+ if (get_user(cp, compat_pages + i))
+ goto out_flush;
+
+ p = compat_ptr(cp);
+ } else {
+ if (get_user(p, pages + i))
+ goto out_flush;
+ }
if (get_user(node, nodes + i))
goto out_flush;