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 <[email protected]>
Cc: [email protected]
Signed-off-by: John Hubbard <[email protected]>
---
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;
fc->global = true;
}
return ctx;
--
2.54.0
