From 6669d1aaa0c45a50a4cc5f1756ab03578eaebd18 Mon Sep 17 00:00:00 2001 From: Lorenzo Stoakes Date: Wed, 14 May 2025 09:40:24 +0100 Subject: [PATCH] mm: remove WARN_ON_ONCE() in file_has_valid_mmap_hooks() Having encountered a trinity report in linux-next (Linked in the 'Closes' tag) it appears that there are legitimate situations where a file-backed mapping can be acquired but no file->f_op->mmap or file->f_op->mmap_prepare is set, at which point do_mmap() should simply error out with -ENODEV. Since previously we did not warn in this scenario and it appears we rely upon this, restore this situation, while retaining a WARN_ON_ONCE() for the case where both are set, which is absolutely incorrect and must be addressed and thus always requires a warning. If further work is required to chase down precisely what is causing this, then we can later restore this, but it makes no sense to hold up this series to do so, as this is existing and apparently expected behaviour. Link: https://lkml.kernel.org/r/20250514084024.29148-1-lorenzo.stoakes@oracle.com Fixes: c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file callback") Signed-off-by: Lorenzo Stoakes Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202505141434.96ce5e5d-lkp@intel.com Reviewed-by: Vlastimil Babka Reviewed-by: Pedro Falcato Acked-by: David Hildenbrand Cc: Al Viro Cc: Christian Brauner Cc: Jan Kara Cc: Jann Horn Cc: Liam Howlett Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton --- include/linux/fs.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index e2721a1ff13da..09c8495dacdbc 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2248,7 +2248,7 @@ static inline bool file_has_valid_mmap_hooks(struct file *file) /* Hooks are mutually exclusive. */ if (WARN_ON_ONCE(has_mmap && has_mmap_prepare)) return false; - if (WARN_ON_ONCE(!has_mmap && !has_mmap_prepare)) + if (!has_mmap && !has_mmap_prepare) return false; return true; -- 2.47.2