This is a note to let you know that I've just added the patch titled
readdir: make sure to verify directory entry for legacy interfaces too
to the 5.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
readdir-make-sure-to-verify-directory-entry-for-legacy-interfaces-too.patch
and it can be found in the queue-5.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0c93ac69407d63a85be0129aa55ffaec27ffebd3 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Sat, 17 Apr 2021 09:27:04 -0700
Subject: readdir: make sure to verify directory entry for legacy interfaces too
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
commit 0c93ac69407d63a85be0129aa55ffaec27ffebd3 upstream.
This does the directory entry name verification for the legacy
"fillonedir" (and compat) interface that goes all the way back to the
dark ages before we had a proper dirent, and the readdir() system call
returned just a single entry at a time.
Nobody should use this interface unless you still have binaries from
1991, but let's do it right.
This came up during discussions about unsafe_copy_to_user() and proper
checking of all the inputs to it, as the networking layer is looking to
use it in a few new places. So let's make sure the _old_ users do it
all right and proper, before we add new ones.
See also commit 8a23eb804ca4 ("Make filldir[64]() verify the directory
entry filename is valid") which did the proper modern interfaces that
people actually use. It had a note:
Note that I didn't bother adding the checks to any legacy interfaces
that nobody uses.
which this now corrects. Note that we really don't care about POSIX and
the presense of '/' in a directory entry, but verify_dirent_name() also
ends up doing the proper name length verification which is what the
input checking discussion was about.
[ Another option would be to remove the support for this particular very
old interface: any binaries that use it are likely a.out binaries, and
they will no longer run anyway since we removed a.out binftm support
in commit eac616557050 ("x86: Deprecate a.out support").
But I'm not sure which came first: getdents() or ELF support, so let's
pretend somebody might still have a working binary that uses the
legacy readdir() case.. ]
Link: https://lore.kernel.org/lkml/CAHk-=wjbvzCAhAtvG0d81W5o0-KT5PPTHhfJ5ieDFq+bGtgOYg@xxxxxxxxxxxxxx/
Acked-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/readdir.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -150,6 +150,9 @@ static int fillonedir(struct dir_context
if (buf->result)
return -EINVAL;
+ buf->result = verify_dirent_name(name, namlen);
+ if (buf->result < 0)
+ return buf->result;
d_ino = ino;
if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
buf->result = -EOVERFLOW;
@@ -405,6 +408,9 @@ static int compat_fillonedir(struct dir_
if (buf->result)
return -EINVAL;
+ buf->result = verify_dirent_name(name, namlen);
+ if (buf->result < 0)
+ return buf->result;
d_ino = ino;
if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
buf->result = -EOVERFLOW;
Patches currently in stable-queue which might be from torvalds@xxxxxxxxxxxxxxxxxxxx are
queue-5.11/lib-fix-kconfig-dependency-on-arch_want_frame_pointe.patch
queue-5.11/readdir-make-sure-to-verify-directory-entry-for-legacy-interfaces-too.patch
