From patchwork Tue Mar 4 05:57:50 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Disseldorp X-Patchwork-Id: 13999976 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9AE5F1F473C for ; Tue, 4 Mar 2025 06:11:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.131 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741068680; cv=none; b=A7P9aCDgdC2A34bO5SmlhAb53mBiIlj2vT/3fFQYpCVPOhHpA4BfpUmA9EB8WCO2Z/q4Zsrm/AJ48hi0GEkfKcEGFvG/J+WekIUTjG3LE5rF24LKeALAug8i/el49zzkxUIt1P/VGS/bD2eL7O5igT8fnRZiBIcxzbo4EWynJ1U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741068680; c=relaxed/simple; bh=s/MLrsZFxuwfkP4egpHy7WZYFKlEtB/YLVrfclejCAw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jPSlOODDBUz72rfP+hK/NKkY99DFjtek4ON2pBMhChsczi3zfQCrDyzX/YQWWOU+fmwG8Bk3CbFZnXblgBjXQNUvGR8IVA5VnlHhgMXteFLKwQGxvZ0x/wsNu6LWVz5Yo6lSpYx5KJ/Q0xzCtdPAtD9zneIw8el3LQrojVUbfXs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de; spf=pass smtp.mailfrom=suse.de; arc=none smtp.client-ip=195.135.223.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.de Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id A69631F74D; Tue, 4 Mar 2025 06:10:51 +0000 (UTC) Authentication-Results: smtp-out2.suse.de; none Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id A10961393C; Tue, 4 Mar 2025 06:10:49 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id UIlWFmmZxmfADQAAD6G6ig (envelope-from ); Tue, 04 Mar 2025 06:10:49 +0000 From: David Disseldorp To: linux-fsdevel@vger.kernel.org Cc: linux-kselftest@vger.kernel.org, Al Viro , Christian Brauner , David Disseldorp Subject: [PATCH v4 7/8] initramfs: fix hardlink hash leak without TRAILER Date: Tue, 4 Mar 2025 16:57:50 +1100 Message-ID: <20250304061020.9815-8-ddiss@suse.de> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250304061020.9815-1-ddiss@suse.de> References: <20250304061020.9815-1-ddiss@suse.de> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spam-Level: X-Spamd-Result: default: False [-4.00 / 50.00]; REPLY(-4.00)[]; ASN(0.00)[asn:25478, ipnet:::/0, country:RU] X-Spam-Score: -4.00 X-Spam-Flag: NO X-Rspamd-Queue-Id: A69631F74D X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Rspamd-Action: no action X-Rspamd-Server: rspamd2.dmz-prg2.suse.org Covered in Documentation/driver-api/early-userspace/buffer-format.rst , initramfs archives can carry an optional "TRAILER!!!" entry which serves as a boundary for collecting and associating hardlinks with matching inode and major / minor device numbers. Although optional, if hardlinks are found in an archive without a subsequent "TRAILER!!!" entry then the hardlink state hash table is leaked, e.g. unfixed kernel, with initramfs_test.c hunk applied only: unreferenced object 0xffff9405408cc000 (size 8192): comm "kunit_try_catch", pid 53, jiffies 4294892519 hex dump (first 32 bytes): 01 00 00 00 01 00 00 00 00 00 00 00 ff 81 00 00 ................ 00 00 00 00 00 00 00 00 69 6e 69 74 72 61 6d 66 ........initramf backtrace (crc a9fb0ee0): [<0000000066739faa>] __kmalloc_cache_noprof+0x11d/0x250 [<00000000fc755219>] maybe_link.part.5+0xbc/0x120 [<000000000526a128>] do_name+0xce/0x2f0 [<00000000145c1048>] write_buffer+0x22/0x40 [<000000003f0b4f32>] unpack_to_rootfs+0xf9/0x2a0 [<00000000d6f7e5af>] initramfs_test_hardlink+0xe3/0x3f0 [<0000000014fde8d6>] kunit_try_run_case+0x5f/0x130 [<00000000dc9dafc5>] kunit_generic_run_threadfn_adapter+0x18/0x30 [<000000001076c239>] kthread+0xc8/0x100 [<00000000d939f1c1>] ret_from_fork+0x2b/0x40 [<00000000f848ad1a>] ret_from_fork_asm+0x1a/0x30 Fix this by calling free_hash() after initramfs buffer processing in unpack_to_rootfs(). An extra hardlink_seen global is added as an optimization to avoid walking the 32 entry hash array unnecessarily. The expectation is that a "TRAILER!!!" entry will normally be present, and initramfs hardlinks are uncommon. There is one user facing side-effect of this fix: hardlinks can currently be associated across built-in and external initramfs archives, *if* the built-in initramfs archive lacks a "TRAILER!!!" terminator. I'd consider this cross-archive association broken, but perhaps it's used. Signed-off-by: David Disseldorp --- init/initramfs.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/init/initramfs.c b/init/initramfs.c index b9cacdc54eaf1..e0b11f8d6f3d6 100644 --- a/init/initramfs.c +++ b/init/initramfs.c @@ -76,6 +76,7 @@ static __initdata struct hash { struct hash *next; char name[N_ALIGN(PATH_MAX)]; } *head[32]; +static __initdata bool hardlink_seen; static inline int hash(int major, int minor, int ino) { @@ -109,19 +110,21 @@ static char __init *find_link(int major, int minor, int ino, strcpy(q->name, name); q->next = NULL; *p = q; + hardlink_seen = true; return NULL; } static void __init free_hash(void) { struct hash **p, *q; - for (p = head; p < head + 32; p++) { + for (p = head; hardlink_seen && p < head + 32; p++) { while (*p) { q = *p; *p = q->next; kfree(q); } } + hardlink_seen = false; } #ifdef CONFIG_INITRAMFS_PRESERVE_MTIME @@ -564,6 +567,8 @@ char * __init unpack_to_rootfs(char *buf, unsigned long len) len -= my_inptr; } dir_utime(); + /* free any hardlink state collected without optional TRAILER!!! */ + free_hash(); kfree(bufs); return message; }