From patchwork Mon Jul 1 22:39:25 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13718687 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 1F381171079; Mon, 1 Jul 2024 22:39:45 +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=1719873586; cv=none; b=dUvJqYf9YxQisEBSJTyYz/9tDEpVPuHE082SSzc1Po50FHj9+kYD1JubjgfSQzIJHLe0xi4MHDF63ps75+Xoi4R8NENE2OL4kTfw2K1y4J4LGM09vltXTg0Yyne0lBS6WUYGcwmRUW2QexflLwHJjKT7LPaJEadSPeQVVEflaoQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719873586; c=relaxed/simple; bh=zuWlQDRIA9Y3TvaGDg+DFpB2kxzINwcItGB/mZydiw8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bT5Hk9Yi4HY/80XU+pfjnbISGdcaQ6ViS18K6c3M8BMc2R4zsV2ujWS72UzBspIL5dNNFqajW/Il21ZXtixgyH0p76KvRlLJeSY12a4XOLQeoO0UQ4z4QprB15zBLxIEwpljdNSDUngp7sJzYUN1wtPrCaZopaxqgmvjBa53k20= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eLtXfHjz; 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="eLtXfHjz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75EB9C116B1; Mon, 1 Jul 2024 22:39:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1719873585; bh=zuWlQDRIA9Y3TvaGDg+DFpB2kxzINwcItGB/mZydiw8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eLtXfHjz/odlDT45j//QKRBfSZNrLhArgaG3JBpHfwbkJp8atnSQqneeMmwtMxl2x PFT+6P4z9S0IOPFbCjK9wNp1tDdv9bZ1CQAdcj1qQF1AAsmIa8Db7RukqCqCMhQAIV yz85GmxmIU8vlZxL4nTcyDTMqqUg/ecOdoDnbVX/p1+gp6SGqRWRXIG/27mL+BCAbW 54nnkj8CC4zVMlJoeBtcY1hYZmzGwxFGTZ6LPj7V58shVr8LarZ7JrpbtsZmeykMAZ ZSiRsYVHI4hSyyqTxw2tRlp1sgkrByQ4g6JXexMDwPno3a/p90tspYrYQ6EwWWdYLF TTkpqALa0wEzw== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, oleg@redhat.com Cc: peterz@infradead.org, mingo@redhat.com, bpf@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, clm@meta.com, Andrii Nakryiko Subject: [PATCH v2 02/12] uprobes: correct mmap_sem locking assumptions in uprobe_write_opcode() Date: Mon, 1 Jul 2024 15:39:25 -0700 Message-ID: <20240701223935.3783951-3-andrii@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240701223935.3783951-1-andrii@kernel.org> References: <20240701223935.3783951-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 It seems like uprobe_write_opcode() doesn't require writer locked mmap_sem, any lock (reader or writer) should be sufficient. This was established in a discussion in [0] and looking through existing code seems to confirm that there is no need for write-locked mmap_sem. Fix the comment to state this clearly. [0] https://lore.kernel.org/linux-trace-kernel/20240625190748.GC14254@redhat.com/ Fixes: 29dedee0e693 ("uprobes: Add mem_cgroup_charge_anon() into uprobe_write_opcode()") Signed-off-by: Andrii Nakryiko Acked-by: Oleg Nesterov --- kernel/events/uprobes.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 081821fd529a..f87049c08ee9 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -453,7 +453,7 @@ static int update_ref_ctr(struct uprobe *uprobe, struct mm_struct *mm, * @vaddr: the virtual address to store the opcode. * @opcode: opcode to be written at @vaddr. * - * Called with mm->mmap_lock held for write. + * Called with mm->mmap_lock held for read or write. * Return 0 (success) or a negative errno. */ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,