fsnotify: pass correct offset to fsnotify_mmap_perm()

fsnotify_mmap_perm() requires a byte offset for the file about to be
mmap'ed.  But it is called from vm_mmap_pgoff(), which has a page offset.
Previously the conversion was done incorrectly so let's fix it, being
careful not to overflow on 32-bit platforms.

Discovered during code review.

Link: https://lkml.kernel.org/r/20251003155238.2147410-1-ryan.roberts@arm.com
Fixes: 066e053fe208 ("fsnotify: add pre-content hooks on mmap()")
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Kiryl Shutsemau <kas@kernel.org>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/util.c b/mm/util.c
index 6c1d64ed02211f0bf113b3ec178a7d78874deff1..8989d57675286199e30ddb693df37c598021c626 100644 (file)
--- a/mm/util.c
+++ b/mm/util.c
@@ -566,6 +566,7 @@ unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
        unsigned long len, unsigned long prot,
        unsigned long flag, unsigned long pgoff)
 {
+       loff_t off = (loff_t)pgoff << PAGE_SHIFT;
        unsigned long ret;
        struct mm_struct *mm = current->mm;
        unsigned long populate;
@@ -573,7 +574,7 @@ unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
 
        ret = security_mmap_file(file, prot, flag);
        if (!ret)
-               ret = fsnotify_mmap_perm(file, prot, pgoff >> PAGE_SHIFT, len);
+               ret = fsnotify_mmap_perm(file, prot, off, len);
        if (!ret) {
                if (mmap_write_lock_killable(mm))
                        return -EINTR;