On Fri, Oct 03, 2025 at 04:58:04PM +0100, Kiryl Shutsemau wrote:
From: Kiryl Shutsemau kas@kernel.org
vm_mmap_pgoff() includes a fsnotify call that allows for pre-content hooks on mmap().
The fsnotify_mmap_perm() function takes, among other arguments, an offset in the file in the form of loff_t. However, vm_mmap_pgoff() has file offset in the form of pgoff. This offset needs to be converted before being passed to fsnotify_mmap_perm().
The conversion from pgoff to loff_t is incorrect. The pgoff value needs to be shifted left by PAGE_SHIFT to obtain loff_t, not right.
This issue was identified through code inspection.
Signed-off-by: Kiryl Shutsemau kas@kernel.org Fixes: 066e053fe208 ("fsnotify: add pre-content hooks on mmap()") Cc: stable@vger.kernel.org Cc: Josef Bacik josef@toxicpanda.com Cc: Amir Goldstein amir73il@gmail.com Cc: Jan Kara jack@suse.cz
mm/util.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/util.c b/mm/util.c index f814e6a59ab1..52a667157264 100644 --- a/mm/util.c +++ b/mm/util.c @@ -573,7 +573,7 @@ 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, pgoff << PAGE_SHIFT, len);
It misses the case to (loff_t) and it broken for 32-bit machines.
Luckily, Ryan submitted another fix for the same bug at the almost the same time. And he was more careful around types:
https://lore.kernel.org/all/20251003155238.2147410-1-ryan.roberts@arm.com