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bh=L5Dt6ifLtfxpQReGiGa8FPtcvrHCrYklyb55VjlPhvY=; b=iYzlIv3GFqFdPT0IGa84nfUaJu VGPW7kWQpgI/N8r9/M7FRK41KuhaqyYWZWIKqzQ4/flNTLrqB1EXIexvCfkHhB/Q12W4Yx72PBf1x JL3V8XAtHp/5Bwu/8gQDQhqigqHPm5d/IaJfC9alsHJaTHN8KZi56HaOhkonF5XAJ/jw=; Received: from mail.kernel.org ([198.145.29.99]) by sfi-mx-3.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.2) id 1iuqOb-00GXd4-UW for linux-f2fs-devel@lists.sourceforge.net; Fri, 24 Jan 2020 04:16:39 +0000 Received: from sol.hsd1.ca.comcast.net (c-107-3-166-239.hsd1.ca.comcast.net [107.3.166.239]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 920902070A; Fri, 24 Jan 2020 04:16:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579839387; bh=kj/UPIlxMTG1LNrRNQzAQibp9tj2WikH8O930HrmAmU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=a67IdEUAnRcrrHdsQK7Nbl5g7OMOKGhUa7H2t42Ofc5V4ViYMbnvhK/a34YlJ+krO vmTgWu/vfSimME2bI6MPvtXho8XRo0ExKGAxkWCy262Xx8CsCGhYC/qMYhcQmegp9w qkPDAlLSC701dz3K1kcrqiHoKDf0AfVYXDtnfgjk= From: Eric Biggers To: linux-f2fs-devel@lists.sourceforge.net Date: Thu, 23 Jan 2020 20:15:49 -0800 Message-Id: <20200124041549.159983-3-ebiggers@kernel.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200124041549.159983-1-ebiggers@kernel.org> References: <20200124041549.159983-1-ebiggers@kernel.org> MIME-Version: 1.0 X-Headers-End: 1iuqOb-00GXd4-UW Subject: [f2fs-dev] [PATCH 2/2] f2fs: fix race conditions in ->d_compare() and ->d_hash() X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Gabriel Krisman Bertazi , Alexander Viro , Daniel Rosenberg Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net From: Eric Biggers Since ->d_compare() and ->d_hash() can be called in RCU-walk mode, ->d_parent and ->d_inode can be concurrently modified, and in particular, ->d_inode may be changed to NULL. For f2fs_d_hash() this resulted in a reproducible NULL dereference if a lookup is done in a directory being deleted, e.g. with: int main() { if (fork()) { for (;;) { mkdir("subdir", 0700); rmdir("subdir"); } } else { for (;;) access("subdir/file", 0); } } ... or by running the 't_encrypted_d_revalidate' program from xfstests. Both repros work in any directory on a filesystem with the encoding feature, even if the directory doesn't actually have the casefold flag. I couldn't reproduce a crash in f2fs_d_compare(), but it appears that a similar crash is possible there. Fix these bugs by reading ->d_parent and ->d_inode using READ_ONCE() and falling back to the case sensitive behavior if the inode is NULL. Reported-by: Al Viro Fixes: 2c2eb7a300cd ("f2fs: Support case-insensitive file name lookups") Cc: # v5.4+ Signed-off-by: Eric Biggers --- fs/f2fs/dir.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index aea9e2806144d..d7c9a2cda4899 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -1083,24 +1083,27 @@ static int f2fs_d_compare(const struct dentry *dentry, unsigned int len, const char *str, const struct qstr *name) { struct qstr qstr = {.name = str, .len = len }; + const struct dentry *parent = READ_ONCE(dentry->d_parent); + const struct inode *inode = READ_ONCE(parent->d_inode); - if (!IS_CASEFOLDED(dentry->d_parent->d_inode)) { + if (!inode || !IS_CASEFOLDED(inode)) { if (len != name->len) return -1; return memcmp(str, name->name, len); } - return f2fs_ci_compare(dentry->d_parent->d_inode, name, &qstr, false); + return f2fs_ci_compare(inode, name, &qstr, false); } static int f2fs_d_hash(const struct dentry *dentry, struct qstr *str) { struct f2fs_sb_info *sbi = F2FS_SB(dentry->d_sb); const struct unicode_map *um = sbi->s_encoding; + const struct inode *inode = READ_ONCE(dentry->d_inode); unsigned char *norm; int len, ret = 0; - if (!IS_CASEFOLDED(dentry->d_inode)) + if (!inode || !IS_CASEFOLDED(inode)) return 0; norm = f2fs_kmalloc(sbi, PATH_MAX, GFP_ATOMIC); -- 2.25.0 _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel