lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [day] [month] [year] [list]
Message-Id: <20230110180037.992664865@linuxfoundation.org>
Date:   Tue, 10 Jan 2023 19:04:28 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        patches@...ts.linux.dev,
        "linux-ext4@...r.kernel.org, Theodore Tso" <tytso@....edu>,
        Eric Biggers <ebiggers@...gle.com>,
        Theodore Ts'o <tytso@....edu>
Subject: [PATCH 5.15 176/290] ext4: fix off-by-one errors in fast-commit block filling

From: Eric Biggers <ebiggers@...nel.org>

From: Eric Biggers <ebiggers@...gle.com>

commit 48a6a66db82b8043d298a630f22c62d43550cae5 upstream.

Due to several different off-by-one errors, or perhaps due to a late
change in design that wasn't fully reflected in the code that was
actually merged, there are several very strange constraints on how
fast-commit blocks are filled with tlv entries:

- tlvs must start at least 10 bytes before the end of the block, even
  though the minimum tlv length is 8.  Otherwise, the replay code will
  ignore them.  (BUG: ext4_fc_reserve_space() could violate this
  requirement if called with a len of blocksize - 9 or blocksize - 8.
  Fortunately, this doesn't seem to happen currently.)

- tlvs must end at least 1 byte before the end of the block.  Otherwise
  the replay code will consider them to be invalid.  This quirk
  contributed to a bug (fixed by an earlier commit) where uninitialized
  memory was being leaked to disk in the last byte of blocks.

Also, strangely these constraints don't apply to the replay code in
e2fsprogs, which will accept any tlvs in the blocks (with no bounds
checks at all, but that is a separate issue...).

Given that this all seems to be a bug, let's fix it by just filling
blocks with tlv entries in the natural way.

Note that old kernels will be unable to replay fast-commit journals
created by kernels that have this commit.

Fixes: aa75f4d3daae ("ext4: main fast-commit commit path")
Cc: <stable@...r.kernel.org> # v5.10+
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Link: https://lore.kernel.org/r/20221106224841.279231-7-ebiggers@kernel.org
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/ext4/fast_commit.c |   66 +++++++++++++++++++++++++-------------------------
 1 file changed, 33 insertions(+), 33 deletions(-)

--- a/fs/ext4/fast_commit.c
+++ b/fs/ext4/fast_commit.c
@@ -643,43 +643,43 @@ static u8 *ext4_fc_reserve_space(struct
 	struct buffer_head *bh;
 	int bsize = sbi->s_journal->j_blocksize;
 	int ret, off = sbi->s_fc_bytes % bsize;
-	int pad_len;
+	int remaining;
 	u8 *dst;
 
 	/*
-	 * After allocating len, we should have space at least for a 0 byte
-	 * padding.
+	 * If 'len' is too long to fit in any block alongside a PAD tlv, then we
+	 * cannot fulfill the request.
 	 */
-	if (len + EXT4_FC_TAG_BASE_LEN > bsize)
+	if (len > bsize - EXT4_FC_TAG_BASE_LEN)
 		return NULL;
 
-	if (bsize - off - 1 > len + EXT4_FC_TAG_BASE_LEN) {
-		/*
-		 * Only allocate from current buffer if we have enough space for
-		 * this request AND we have space to add a zero byte padding.
-		 */
-		if (!sbi->s_fc_bh) {
-			ret = jbd2_fc_get_buf(EXT4_SB(sb)->s_journal, &bh);
-			if (ret)
-				return NULL;
-			sbi->s_fc_bh = bh;
-		}
-		sbi->s_fc_bytes += len;
-		return sbi->s_fc_bh->b_data + off;
+	if (!sbi->s_fc_bh) {
+		ret = jbd2_fc_get_buf(EXT4_SB(sb)->s_journal, &bh);
+		if (ret)
+			return NULL;
+		sbi->s_fc_bh = bh;
 	}
-	/* Need to add PAD tag */
 	dst = sbi->s_fc_bh->b_data + off;
+
+	/*
+	 * Allocate the bytes in the current block if we can do so while still
+	 * leaving enough space for a PAD tlv.
+	 */
+	remaining = bsize - EXT4_FC_TAG_BASE_LEN - off;
+	if (len <= remaining) {
+		sbi->s_fc_bytes += len;
+		return dst;
+	}
+
+	/*
+	 * Else, terminate the current block with a PAD tlv, then allocate a new
+	 * block and allocate the bytes at the start of that new block.
+	 */
+
 	tl.fc_tag = cpu_to_le16(EXT4_FC_TAG_PAD);
-	pad_len = bsize - off - 1 - EXT4_FC_TAG_BASE_LEN;
-	tl.fc_len = cpu_to_le16(pad_len);
+	tl.fc_len = cpu_to_le16(remaining);
 	ext4_fc_memcpy(sb, dst, &tl, EXT4_FC_TAG_BASE_LEN, crc);
-	dst += EXT4_FC_TAG_BASE_LEN;
-	if (pad_len > 0) {
-		ext4_fc_memzero(sb, dst, pad_len, crc);
-		dst += pad_len;
-	}
-	/* Don't leak uninitialized memory in the unused last byte. */
-	*dst = 0;
+	ext4_fc_memzero(sb, dst + EXT4_FC_TAG_BASE_LEN, remaining, crc);
 
 	ext4_fc_submit_bh(sb, false);
 
@@ -687,7 +687,7 @@ static u8 *ext4_fc_reserve_space(struct
 	if (ret)
 		return NULL;
 	sbi->s_fc_bh = bh;
-	sbi->s_fc_bytes = (sbi->s_fc_bytes / bsize + 1) * bsize + len;
+	sbi->s_fc_bytes += bsize - off + len;
 	return sbi->s_fc_bh->b_data;
 }
 
@@ -718,7 +718,7 @@ static int ext4_fc_write_tail(struct sup
 	off = sbi->s_fc_bytes % bsize;
 
 	tl.fc_tag = cpu_to_le16(EXT4_FC_TAG_TAIL);
-	tl.fc_len = cpu_to_le16(bsize - off - 1 + sizeof(struct ext4_fc_tail));
+	tl.fc_len = cpu_to_le16(bsize - off + sizeof(struct ext4_fc_tail));
 	sbi->s_fc_bytes = round_up(sbi->s_fc_bytes, bsize);
 
 	ext4_fc_memcpy(sb, dst, &tl, EXT4_FC_TAG_BASE_LEN, &crc);
@@ -1981,7 +1981,7 @@ static int ext4_fc_replay_scan(journal_t
 	state = &sbi->s_fc_replay_state;
 
 	start = (u8 *)bh->b_data;
-	end = (__u8 *)bh->b_data + journal->j_blocksize - 1;
+	end = start + journal->j_blocksize;
 
 	if (state->fc_replay_expected_off == 0) {
 		state->fc_cur_tag = 0;
@@ -2002,7 +2002,7 @@ static int ext4_fc_replay_scan(journal_t
 	}
 
 	state->fc_replay_expected_off++;
-	for (cur = start; cur < end - EXT4_FC_TAG_BASE_LEN;
+	for (cur = start; cur <= end - EXT4_FC_TAG_BASE_LEN;
 	     cur = cur + EXT4_FC_TAG_BASE_LEN + tl.fc_len) {
 		ext4_fc_get_tl(&tl, cur);
 		val = cur + EXT4_FC_TAG_BASE_LEN;
@@ -2120,9 +2120,9 @@ static int ext4_fc_replay(journal_t *jou
 #endif
 
 	start = (u8 *)bh->b_data;
-	end = (__u8 *)bh->b_data + journal->j_blocksize - 1;
+	end = start + journal->j_blocksize;
 
-	for (cur = start; cur < end - EXT4_FC_TAG_BASE_LEN;
+	for (cur = start; cur <= end - EXT4_FC_TAG_BASE_LEN;
 	     cur = cur + EXT4_FC_TAG_BASE_LEN + tl.fc_len) {
 		ext4_fc_get_tl(&tl, cur);
 		val = cur + EXT4_FC_TAG_BASE_LEN;


Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ