From: Linus Torvalds torvalds@linux-foundation.org
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+bGt... Acked-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/readdir.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/fs/readdir.c +++ b/fs/readdir.c @@ -133,6 +133,9 @@ 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; @@ -392,6 +395,9 @@ 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;