5.15-stable review patch. If anyone has any objections, please let me know.
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From: Gregory Price gourry.memverge@gmail.com
commit 229e2253766c7cdfe024f1fe280020cc4711087c upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/migrate.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)
--- a/mm/migrate.c +++ b/mm/migrate.c @@ -1788,6 +1788,7 @@ static int do_pages_move(struct mm_struc 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; @@ -1801,8 +1802,17 @@ static int do_pages_move(struct mm_struc 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; addr = (unsigned long)untagged_addr(p);