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 4B2CB2319E3; Fri, 29 Mar 2024 12:46:19 +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=1711716379; cv=none; b=C/yiyasQ+uESKwcloHzykoRVmeSa/QUeF0vaOR8ANqdStGsklajFNSwcP4iNJ4Va8Zlx5OJdPbq1cqMDlrTEkXRE50I9nkoZkZMSUWzMPCFS6omcOkTclYp/wmsWoVs6ZsMuHmT3Xhn7hW9BQbmYvEc9xcO9JPP/QGB74IPlsDE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711716379; c=relaxed/simple; bh=fYnV1nzJqLf47M7t6VkglOE/shdEqI3JuCSeJTpHvKM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cOaalEoeo3ZFHITcXp+rwcVgE+3OUp2z/Mlzpq4b5lAPi/d+Fs4PJrWJSjY6cEK6t70ekizT0MSy+0xFnCPyiVZYIqBOz9tc3sibOkNGtANrYc4LzGj2zFsBFQql80gd3AyXMAdJWuWFfRq7FvmAx8/8rW7n59P74rHvsH0QITY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HJ7Tdf5t; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HJ7Tdf5t" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C348CC433F1; Fri, 29 Mar 2024 12:46:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711716379; bh=fYnV1nzJqLf47M7t6VkglOE/shdEqI3JuCSeJTpHvKM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HJ7Tdf5tL7rTHdEilbyPYEuyVpI+JJV+gP/C0kdmm+SDN4NkQ9pgQek7wOSdEPg4b BkE8aWPjru2gT3evKMzH9TAgIi4AUs1nHyp1ik70Ze+j1te1BG7+QOLD53jBwt/j1v r3to430sVn6QQzWQ9e3iD98v8gs1px3KNwYPV8Yv0muz9XV7vVySvEx9nDj5xbVAxh Xv7JcgDKsW5AGQnd207NzHZ8k2jpeUhyksgIWOIfWIm2r2DK2RE6zVyOOVn5pDTYOz lnLFASNcB0SvQ44BxKYmoe0sdUY6dTVna8w+5NC6L9lBCGTKJhwkoX/pAz9v+CMbw3 LhhOOqo170JLw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Tetsuo Handa , syzbot , Al Viro , Christian Brauner , Sasha Levin , jlayton@kernel.org, jack@suse.cz, princekumarmaurya06@gmail.com, pc@manguebit.com, willy@infradead.org Subject: [PATCH AUTOSEL 6.1 08/52] sysv: don't call sb_bread() with pointers_lock held Date: Fri, 29 Mar 2024 08:45:02 -0400 Message-ID: <20240329124605.3091273-8-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240329124605.3091273-1-sashal@kernel.org> References: <20240329124605.3091273-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.1.83 Content-Transfer-Encoding: 8bit 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 9925cfe571595..17c7d76770a0a 100644 --- a/fs/sysv/itree.c +++ b/fs/sysv/itree.c @@ -82,9 +82,6 @@ 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[], @@ -104,15 +101,18 @@ 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; @@ -218,9 +218,7 @@ 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) { @@ -290,9 +288,9 @@ 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