The core routine get_unmapped_area will call a filesystem specific version of get_unmapped_area if it exists in file operations. If a file is on a union/overlay, overlayfs does not contain a get_unmapped_area f_op and the underlying filesystem routine may be ignored. Add an overlayfs f_op to call the underlying f_op if it exists.
The routine is_file_hugetlbfs() is used to determine if a file is on hugetlbfs. This is determined by f_mode & FMODE_HUGETLBFS. Copy the mode to the overlayfs file during open so that is_file_hugetlbfs() will work as intended. These two issues can result in the BUG as shown in [1]. [1] https://lore.kernel.org/linux-mm/000000000000b4684e05a2968...@google.com/ Reported-by: syzbot+d6ec23007e951dadf...@syzkaller.appspotmail.com Signed-off-by: Miklos Szeredi <mik...@szeredi.hu> Signed-off-by: Mike Kravetz <mike.krav...@oracle.com> --- fs/overlayfs/file.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index 87c362f65448..41e5746ba3c6 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -124,6 +124,8 @@ static int ovl_real_fdget(const struct file *file, struct fd *real) return ovl_real_fdget_meta(file, real, false); } +#define OVL_F_MODE_TO_UPPER (FMODE_HUGETLBFS) + static int ovl_open(struct inode *inode, struct file *file) { struct file *realfile; @@ -140,6 +142,9 @@ static int ovl_open(struct inode *inode, struct file *file) if (IS_ERR(realfile)) return PTR_ERR(realfile); + /* Copy modes from underlying file */ + file->f_mode |= (realfile->f_mode & OVL_F_MODE_TO_UPPER); + file->private_data = realfile; return 0; @@ -757,6 +762,21 @@ static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in, remap_flags, op); } +#ifdef CONFIG_MMU +static unsigned long ovl_get_unmapped_area(struct file *file, + unsigned long uaddr, unsigned long len, + unsigned long pgoff, unsigned long flags) +{ + struct file *realfile = file->private_data; + + return (realfile->f_op->get_unmapped_area ?: + current->mm->get_unmapped_area)(realfile, + uaddr, len, pgoff, flags); +} +#else +#define ovl_get_unmapped_area NULL +#endif + const struct file_operations ovl_file_operations = { .open = ovl_open, .release = ovl_release, @@ -774,6 +794,7 @@ const struct file_operations ovl_file_operations = { .copy_file_range = ovl_copy_file_range, .remap_file_range = ovl_remap_file_range, + .get_unmapped_area = ovl_get_unmapped_area, }; int __init ovl_aio_request_cache_init(void) -- 2.25.4
