From: Baoquan He <bhe@redhat.com> stable inclusion from stable-v6.6.88 commit 006b67ac61312fe2be05f33acb3f9473df6a7416 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14806 CVE: CVE-2026-43262 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 8c03ebd7cdc06bd0d2fecb4d1a609ef1dbb7d0aa upstream. Not like fault_in_readable() or fault_in_writeable(), in fault_in_safe_writeable() local variable 'start' is increased page by page to loop till the whole address range is handled. However, it mistakenly calculates the size of the handled range with 'uaddr - start'. Fix it here. Andreas said: : In gfs2, fault_in_iov_iter_writeable() is used in : gfs2_file_direct_read() and gfs2_file_read_iter(), so this potentially : affects buffered as well as direct reads. This bug could cause those : gfs2 functions to spin in a loop. Link: https://lkml.kernel.org/r/20250410035717.473207-1-bhe@redhat.com Link: https://lkml.kernel.org/r/20250410035717.473207-2-bhe@redhat.com Signed-off-by: Baoquan He <bhe@redhat.com> Fixes: fe673d3f5bf1 ("mm: gup: make fault_in_safe_writeable() use fixup_user_fault()") Reviewed-by: Oscar Salvador <osalvador@suse.de> Acked-by: David Hildenbrand <david@redhat.com> Cc: Andreas Gruenbacher <agruenba@redhat.com> Cc: Yanjun.Zhu <yanjun.zhu@linux.dev> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Hongbo Li <lihongbo22@huawei.com> --- mm/gup.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 5f9b56a768c8..2bdb357f44ff 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1670,8 +1670,8 @@ size_t fault_in_safe_writeable(const char __user *uaddr, size_t size) } while (start != end); mmap_read_unlock(mm); - if (size > (unsigned long)uaddr - start) - return size - ((unsigned long)uaddr - start); + if (size > start - (unsigned long)uaddr) + return size - (start - (unsigned long)uaddr); return 0; } EXPORT_SYMBOL(fault_in_safe_writeable); -- 2.34.1