FAILED: patch "[PATCH] f2fs: avoid utf8_strncasecmp() with unstable name" failed to apply to 5.7-stable tree

FAILED: patch "[PATCH] f2fs: avoid utf8_strncasecmp() with unstable name" failed to apply to 5.7-stable tree

[gregkh]

The patch below does not apply to the 5.7-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From fc3bb095ab02b9e7d89a069ade2cead15c64c504 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Mon, 1 Jun 2020 13:08:05 -0700
Subject: [PATCH] f2fs: avoid utf8_strncasecmp() with unstable name

If the dentry name passed to ->d_compare() fits in dentry::d_iname, then
it may be concurrently modified by a rename.  This can cause undefined
behavior (possibly out-of-bounds memory accesses or crashes) in
utf8_strncasecmp(), since fs/unicode/ isn't written to handle strings
that may be concurrently modified.

Fix this by first copying the filename to a stack buffer if needed.
This way we get a stable snapshot of the filename.

Fixes: 2c2eb7a300cd ("f2fs: Support case-insensitive file name lookups")
Cc: <stable@vger.kernel.org> # v5.4+
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Daniel Rosenberg <drosen@google.com>
Cc: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index 29f70f2295cc..d35976785e8c 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -1114,11 +1114,27 @@ static int f2fs_d_compare(const struct dentry *dentry, unsigned int len,
 	const struct inode *dir = READ_ONCE(parent->d_inode);
 	const struct f2fs_sb_info *sbi = F2FS_SB(dentry->d_sb);
 	struct qstr entry = QSTR_INIT(str, len);
+	char strbuf[DNAME_INLINE_LEN];
 	int res;
 
 	if (!dir || !IS_CASEFOLDED(dir))
 		goto fallback;
 
+	/*
+	 * If the dentry name is stored in-line, then it may be concurrently
+	 * modified by a rename.  If this happens, the VFS will eventually retry
+	 * the lookup, so it doesn't matter what ->d_compare() returns.
+	 * However, it's unsafe to call utf8_strncasecmp() with an unstable
+	 * string.  Therefore, we have to copy the name into a temporary buffer.
+	 */
+	if (len <= DNAME_INLINE_LEN - 1) {
+		memcpy(strbuf, str, len);
+		strbuf[len] = 0;
+		entry.name = strbuf;
+		/* prevent compiler from optimizing out the temporary buffer */
+		barrier();
+	}
+
 	res = utf8_strncasecmp(sbi->s_encoding, name, &entry);
 	if (res >= 0)
 		return res;

Re: FAILED: patch "[PATCH] f2fs: avoid utf8_strncasecmp() with unstable name" failed to apply to 5.7-stable tree

[Sasha Levin]

On Fri, Jun 19, 2020 at 04:06:23PM +0200, gregkh@linuxfoundation.org wrote:
>
>The patch below does not apply to the 5.7-stable tree.
>If someone wants it applied there, or to any other stable or longterm
>tree, then please email the backport, including the original git commit
>id to <stable@vger.kernel.org>.
>
>thanks,
>
>greg k-h
>
>------------------ original commit in Linus's tree ------------------
>
>From fc3bb095ab02b9e7d89a069ade2cead15c64c504 Mon Sep 17 00:00:00 2001
>From: Eric Biggers <ebiggers@google.com>
>Date: Mon, 1 Jun 2020 13:08:05 -0700
>Subject: [PATCH] f2fs: avoid utf8_strncasecmp() with unstable name
>
>If the dentry name passed to ->d_compare() fits in dentry::d_iname, then
>it may be concurrently modified by a rename.  This can cause undefined
>behavior (possibly out-of-bounds memory accesses or crashes) in
>utf8_strncasecmp(), since fs/unicode/ isn't written to handle strings
>that may be concurrently modified.
>
>Fix this by first copying the filename to a stack buffer if needed.
>This way we get a stable snapshot of the filename.
>
>Fixes: 2c2eb7a300cd ("f2fs: Support case-insensitive file name lookups")
>Cc: <stable@vger.kernel.org> # v5.4+
>Cc: Al Viro <viro@zeniv.linux.org.uk>
>Cc: Daniel Rosenberg <drosen@google.com>
>Cc: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
>Signed-off-by: Eric Biggers <ebiggers@google.com>
>Reviewed-by: Chao Yu <yuchao0@huawei.com>
>Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

I've grabbed f874fa1c7c79 ("f2fs: split f2fs_d_compare() from
f2fs_match_name()") as a dependency and queued both for 5.7 and 5.4.

-- 
Thanks,
Sasha

Re: FAILED: patch "[PATCH] f2fs: avoid utf8_strncasecmp() with unstable name" failed to apply to 5.7-stable tree

[Greg KH]

On Mon, Jun 22, 2020 at 09:29:48PM -0400, Sasha Levin wrote:
> On Fri, Jun 19, 2020 at 04:06:23PM +0200, gregkh@linuxfoundation.org wrote:
> > 
> > The patch below does not apply to the 5.7-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@vger.kernel.org>.
> > 
> > thanks,
> > 
> > greg k-h
> > 
> > ------------------ original commit in Linus's tree ------------------
> > 
> > > From fc3bb095ab02b9e7d89a069ade2cead15c64c504 Mon Sep 17 00:00:00 2001
> > From: Eric Biggers <ebiggers@google.com>
> > Date: Mon, 1 Jun 2020 13:08:05 -0700
> > Subject: [PATCH] f2fs: avoid utf8_strncasecmp() with unstable name
> > 
> > If the dentry name passed to ->d_compare() fits in dentry::d_iname, then
> > it may be concurrently modified by a rename.  This can cause undefined
> > behavior (possibly out-of-bounds memory accesses or crashes) in
> > utf8_strncasecmp(), since fs/unicode/ isn't written to handle strings
> > that may be concurrently modified.
> > 
> > Fix this by first copying the filename to a stack buffer if needed.
> > This way we get a stable snapshot of the filename.
> > 
> > Fixes: 2c2eb7a300cd ("f2fs: Support case-insensitive file name lookups")
> > Cc: <stable@vger.kernel.org> # v5.4+
> > Cc: Al Viro <viro@zeniv.linux.org.uk>
> > Cc: Daniel Rosenberg <drosen@google.com>
> > Cc: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > Reviewed-by: Chao Yu <yuchao0@huawei.com>
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> 
> I've grabbed f874fa1c7c79 ("f2fs: split f2fs_d_compare() from
> f2fs_match_name()") as a dependency and queued both for 5.7 and 5.4.

Thanks for this fix, and the other fixes for the FAILED patches you have
queued up.

greg k-h