From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4EBC3142624; Thu, 11 Apr 2024 10:09:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712830193; cv=none; b=t0h3sn/PGJj5uML7vxs/05WB97jPUsyEq7sMfvxZpK5DIvI1J0y1pt29iIBFV8qyHXkYQJGy/ZGEHPV4B8u3a/EzCK2sZngdcZfbiiAvzs+pShjKn3DdLnnBQlJ1Is5HyxFmPnnchH2H9+FoAcdStAaEj2pPAQ+5HJnRsEiZD0Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712830193; c=relaxed/simple; bh=j8bEXFWjH4u7WCDyUFhxLK3fgidx7BdDrJ0WSx+tAwE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=e9aODmDOWcQRQhJuJoj5E2iuxEwuH7/wztqsB9yrA6SetwTvnuZQ9yhinRsZVqRN/Mh7cmQ9ZQeThuCvpZ/FT85bcu+L0MZ0ouku6fCGwXpWfxLAXXD0F1/1uObEa9u8eoo6IjKm/kc2nBYa6AfFxtUBlnDPr1bR9ZphSwitWz4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vBhbLslZ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="vBhbLslZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5215C433F1; Thu, 11 Apr 2024 10:09:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1712830193; bh=j8bEXFWjH4u7WCDyUFhxLK3fgidx7BdDrJ0WSx+tAwE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vBhbLslZ8ao6MiNdMxkbzQOuIzmIeZ+UIL/uBVnxyI55LaeY1g2Q5k2p+BXpl1dbB fyCFLtt0tuqLfvID79rDirdWKWHXl8hXEakgwA71XjpVUQ+/LjX5zOqht32tvLIoxu EQSG229YxfkcR7ENPgkEsfr3LvAwx1LMELEHGOYY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot , Al Viro , Tetsuo Handa , Christian Brauner , Sasha Levin Subject: [PATCH 6.8 067/143] sysv: dont call sb_bread() with pointers_lock held Date: Thu, 11 Apr 2024 11:55:35 +0200 Message-ID: <20240411095422.932083595@linuxfoundation.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240411095420.903937140@linuxfoundation.org> References: <20240411095420.903937140@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tetsuo Handa [ Upstream commit f123dc86388cb669c3d6322702dc441abc35c31e ] syzbot is reporting sleep in atomic context in SysV filesystem [1], for sb_bread() is called with rw_spinlock held. A "write_lock(&pointers_lock) => read_lock(&pointers_lock) deadlock" bug and a "sb_bread() with write_lock(&pointers_lock)" bug were introduced by "Replace BKL for chain locking with sysvfs-private rwlock" in Linux 2.5.12. Then, "[PATCH] err1-40: sysvfs locking fix" in Linux 2.6.8 fixed the former bug by moving pointers_lock lock to the callers, but instead introduced a "sb_bread() with read_lock(&pointers_lock)" bug (which made this problem easier to hit). Al Viro suggested that why not to do like get_branch()/get_block()/ find_shared() in Minix filesystem does. And doing like that is almost a revert of "[PATCH] err1-40: sysvfs locking fix" except that get_branch() from with find_shared() is called without write_lock(&pointers_lock). Reported-by: syzbot Link: https://syzkaller.appspot.com/bug?extid=69b40dc5fd40f32c199f Suggested-by: Al Viro Signed-off-by: Tetsuo Handa Link: https://lore.kernel.org/r/0d195f93-a22a-49a2-0020-103534d6f7f6@I-love.SAKURA.ne.jp Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin --- fs/sysv/itree.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/fs/sysv/itree.c b/fs/sysv/itree.c index 410ab2a44d2f6..19bcb51a22036 100644 --- a/fs/sysv/itree.c +++ b/fs/sysv/itree.c @@ -83,9 +83,6 @@ static inline sysv_zone_t *block_end(struct buffer_head *bh) return (sysv_zone_t*)((char*)bh->b_data + bh->b_size); } -/* - * Requires read_lock(&pointers_lock) or write_lock(&pointers_lock) - */ static Indirect *get_branch(struct inode *inode, int depth, int offsets[], @@ -105,15 +102,18 @@ static Indirect *get_branch(struct inode *inode, bh = sb_bread(sb, block); if (!bh) goto failure; + read_lock(&pointers_lock); if (!verify_chain(chain, p)) goto changed; add_chain(++p, bh, (sysv_zone_t*)bh->b_data + *++offsets); + read_unlock(&pointers_lock); if (!p->key) goto no_block; } return NULL; changed: + read_unlock(&pointers_lock); brelse(bh); *err = -EAGAIN; goto no_block; @@ -219,9 +219,7 @@ static int get_block(struct inode *inode, sector_t iblock, struct buffer_head *b goto out; reread: - read_lock(&pointers_lock); partial = get_branch(inode, depth, offsets, chain, &err); - read_unlock(&pointers_lock); /* Simplest case - block found, no allocation needed */ if (!partial) { @@ -291,9 +289,9 @@ static Indirect *find_shared(struct inode *inode, *top = 0; for (k = depth; k > 1 && !offsets[k-1]; k--) ; + partial = get_branch(inode, k, offsets, chain, &err); write_lock(&pointers_lock); - partial = get_branch(inode, k, offsets, chain, &err); if (!partial) partial = chain + k-1; /* -- 2.43.0