On Wed 03-06-26 19:53:14, John Hubbard wrote:
Since commit 1e7ab6f67824 ("anon_inode: rework assertions"), path_noexec() warns when an anonymous-inode file is mmap'd from a superblock that has not set SB_I_NOEXEC. dma-buf backs its files this way and never set the flag, so mmap of any exported buffer trips the warning on a CONFIG_DEBUG_VFS=y kernel:
WARNING: CPU: 11 PID: 121813 at fs/exec.c:118 path_noexec+0x47/0x50 do_mmap+0x2b5/0x680 vm_mmap_pgoff+0x129/0x210 ksys_mmap_pgoff+0x177/0x240 __x64_sys_mmap+0x33/0x70
init_pseudo() sets up internal SB_NOUSER mounts that are never path-reachable. Set both flags here so every pseudo filesystem gets them by default instead of each caller setting them.
SB_I_NODEV is inert for unreachable mounts. SB_I_NOEXEC has one visible effect: an executable mapping of a pseudo-fs fd, such as a dma-buf, now fails with -EPERM, which is the invariant the assertion enforces. No in-tree caller maps these executable.
Reproduce on CONFIG_DEBUG_VFS=y:
make -C tools/testing/selftests/dmabuf-heaps sudo ./tools/testing/selftests/dmabuf-heaps/dmabuf-heap -t system
Fixes: 1e7ab6f67824 ("anon_inode: rework assertions") Suggested-by: Christoph Hellwig hch@infradead.org Cc: stable@vger.kernel.org Signed-off-by: John Hubbard jhubbard@nvidia.com
Looks good. Feel free to add:
Reviewed-by: Jan Kara jack@suse.cz
Honza
fs/libfs.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/fs/libfs.c b/fs/libfs.c index 1bbea5e7bae3..e8226b9e1bc8 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -736,6 +736,7 @@ struct pseudo_fs_context *init_pseudo(struct fs_context *fc, fc->fs_private = ctx; fc->ops = &pseudo_fs_context_ops; fc->sb_flags |= SB_NOUSER;
fc->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;-- 2.54.0