Detecting that a mount point has noexec set before calling exec() on a file?

Question

My program calls exec() on a binary that has been written to a directory specified by the user. If the directory resides in a tree mounted with "noexec", the exec() fails with EACCES.

Instead of failing the exec(), I would like to be able to figure out if a directory was mounted with noexec, but none of fcntl(), stat() or mount() return this info (from reading the manpages). Looking at the kernel source for the exec system call, it looks like this info is stored in the metadata of the inode, and I don't see this info being returned from any system call.

 673     struct nameidata nd;
 (..)
 677     err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd, FMODE_READ|FMODE_EXEC);
 678     file = ERR_PTR(err);
 (..)
 682         file = ERR_PTR(-EACCES);
 683         if (!(nd.mnt->mnt_flags & MNT_NOEXEC) &&
 684             S_ISREG(inode->i_mode)) {

Does anyone know of a way to do this?

Thanks.

Answer 1

You can use statvfs()

struct statvfs st;
inr rc = statvfs("/mnt/foo", &st);
if (rc == -1)
   error();
if (st.f_flag & ST_NOEXEC) {
 //no exec flags was set
}