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vfs: Generalize filesystem nodev handling.

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Introduce a function may_open_dev that tests MNT_NODEV and a new
superblock flab SB_I_NODEV.  Use this new function in all of the
places where MNT_NODEV was previously tested.

Add the new SB_I_NODEV s_iflag to proc, sysfs, and mqueuefs as those
filesystems should never support device nodes, and a simple superblock
flags makes that very hard to get wrong.  With SB_I_NODEV set if any
device nodes somehow manage to show up on on a filesystem those
device nodes will be unopenable.

Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman
2016-06-09 15:34:02 -05:00
parent 3ee690143c
commit a2982cc922
6 changed files with 15 additions and 7 deletions
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4
fs/proc/inode.c
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@@ -466,8 +466,8 @@ int proc_fill_super(struct super_block *s, void *data, int silent)
if (!proc_parse_options(data, ns))
return -EINVAL;
/* User space would break if executables appear on proc */
s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC;
/* User space would break if executables or devices appear on proc */
s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
s->s_blocksize = 1024;
s->s_blocksize_bits = 10;