Re: [PATCH] Userfaultfd: Avoid double free of userfault_ctx and remove O_CLOEXEC

[Eric Biggers]

On Tue, Aug 04, 2020 at 01:31:55PM -0700, Lokesh Gidra wrote:
> when get_unused_fd_flags returns error, ctx will be freed by
> userfaultfd's release function, which is indirectly called by fput().
> Also, if anon_inode_getfile_secure() returns an error, then
> userfaultfd_ctx_put() is called, which calls mmdrop() and frees ctx.
> 
> Also, the O_CLOEXEC was inadvertently added to the call to
> get_unused_fd_flags() [1].
> 
> Adding Al Viro's suggested-by, based on [2].
> 
> [1] https://lore.kernel.org/lkml/1f69c0ab-5791-974f-8bc0-3997ab1d61ea@xxxxxxxxxx/
> [2] https://lore.kernel.org/lkml/20200719165746.GJ2786714@xxxxxxxxxxxxxxxxxx/
> 
> Fixes: d08ac70b1e0d (Wire UFFD up to SELinux)
> Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Reported-by: syzbot+75867c44841cb6373570@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Lokesh Gidra <lokeshgidra@xxxxxxxxxx>

What branch does this patch apply to?  Neither mainline nor linux-next works.

- Eric