From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Sasha Levin <sashal@kernel.org>,
linux-fsdevel@vger.kernel.org
Subject: [PATCH AUTOSEL 5.11 23/23] readdir: make sure to verify directory entry for legacy interfaces too
Date: Mon, 19 Apr 2021 16:43:42 -0400 [thread overview]
Message-ID: <20210419204343.6134-23-sashal@kernel.org> (raw)
In-Reply-To: <20210419204343.6134-1-sashal@kernel.org>
From: Linus Torvalds <torvalds@linux-foundation.org>
[ Upstream commit 0c93ac69407d63a85be0129aa55ffaec27ffebd3 ]
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@mail.gmail.com/
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/readdir.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/readdir.c b/fs/readdir.c
index 19434b3c982c..09e8ed7d4161 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -150,6 +150,9 @@ static int fillonedir(struct dir_context *ctx, const char *name, int namlen,
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_context *ctx, const char *name,
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;
--
2.30.2
parent reply other threads:[~2021-04-19 20:44 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <20210419204343.6134-1-sashal@kernel.org>]
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