6.15-stable review patch. If anyone has any objections, please let me know.
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From: Christian Brauner brauner@kernel.org
commit 1ed95281c0c77dbb1540f9855cd3c5f19900f7a5 upstream.
It isn't possible to execute anonymous inodes because they cannot be opened in any way after they have been created. This includes execution:
execveat(fd_anon_inode, "", NULL, NULL, AT_EMPTY_PATH)
Anonymous inodes have inode->f_op set to no_open_fops which sets no_open() which returns ENXIO. That means any call to do_dentry_open() which is the endpoint of the do_open_execat() will fail. There's no chance to execute an anonymous inode. Unless a given subsystem overrides it ofc.
However, we should still harden this and raise SB_I_NODEV and SB_I_NOEXEC on the superblock itself so that no one gets any creative ideas.
Link: https://lore.kernel.org/20250407-work-anon_inode-v1-5-53a44c20d44e@kernel.or... Reviewed-by: Jeff Layton jlayton@kernel.org Cc: stable@vger.kernel.org # all LTS kernels Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/anon_inodes.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/fs/anon_inodes.c +++ b/fs/anon_inodes.c @@ -86,6 +86,8 @@ static int anon_inodefs_init_fs_context( struct pseudo_fs_context *ctx = init_pseudo(fc, ANON_INODE_FS_MAGIC); if (!ctx) return -ENOMEM; + fc->s_iflags |= SB_I_NOEXEC; + fc->s_iflags |= SB_I_NODEV; ctx->dops = &anon_inodefs_dentry_operations; return 0; }