proc: revalidate misc dentries
authorAlexey Dobriyan <adobriyan@gmail.com>
Fri, 13 Apr 2018 22:35:42 +0000 (15:35 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 14 Apr 2018 00:10:27 +0000 (17:10 -0700)
commit1da4d377f943fe4194ffb9fb9c26cc58fad4dd24
treeaed9f3e163f7ecbe85351b92e32ba66a7301c97b
parenta9f2a846f0503e7d729f552e3ccfe2279010fe94
proc: revalidate misc dentries

If module removes proc directory while another process pins it by
chdir'ing to it, then subsequent recreation of proc entry and all
entries down the tree will not be visible to any process until pinning
process unchdir from directory and unpins everything.

Steps to reproduce:

proc_mkdir("aaa", NULL);
proc_create("aaa/bbb", ...);

chdir("/proc/aaa");

remove_proc_entry("aaa/bbb", NULL);
remove_proc_entry("aaa", NULL);

proc_mkdir("aaa", NULL);
# inaccessible because "aaa" dentry still points
# to the original "aaa".
proc_create("aaa/bbb", ...);

Fix is to implement ->d_revalidate and ->d_delete.

Link: http://lkml.kernel.org/r/20180312201938.GA4871@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/proc/generic.c