The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Possible dependencies:
48a6a66db82b ("ext4: fix off-by-one errors in fast-commit block filling") 8415ce07ecf0 ("ext4: fix unaligned memory access in ext4_fc_reserve_space()") 594bc43b4103 ("ext4: fix leaking uninitialized memory in fast-commit journal") 1b45cc5c7b92 ("ext4: fix potential out of bound read in ext4_fc_replay_scan()") dcc5827484d6 ("ext4: factor out ext4_fc_get_tl()") fdc2a3c75dd8 ("ext4: introduce EXT4_FC_TAG_BASE_LEN helper") ccbf8eeb39f2 ("ext4: fix miss release buffer head in ext4_fc_write_inode") 4978c659e7b5 ("ext4: use ext4_debug() instead of jbd_debug()") d9bf099cb980 ("ext4: add commit_tid info in jbd debug log") 0915e464cb27 ("ext4: simplify updating of fast commit stats") 7bbbe241ec7c ("ext4: drop ineligible txn start stop APIs") 02f310fcf47f ("ext4: Speedup ext4 orphan inode handling") 25c6d98fc4c2 ("ext4: Move orphan inode handling into a separate file") 188c299e2a26 ("ext4: Support for checksumming from journal triggers") bd2c38cf1726 ("ext4: Make sure quota files are not grabbed accidentally") facec450a824 ("ext4: reduce arguments of ext4_fc_add_dentry_tlv") b9a037b7f3c4 ("ext4: cleanup in-core orphan list if ext4_truncate() failed to get a transaction handle") a7ba36bc94f2 ("ext4: fix fast commit alignment issues") fcdf3c34b7ab ("ext4: fix debug format string warning") 3088e5a5153c ("ext4: fix various seppling typos")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 48a6a66db82b8043d298a630f22c62d43550cae5 Mon Sep 17 00:00:00 2001 From: Eric Biggers ebiggers@google.com Date: Sun, 6 Nov 2022 14:48:40 -0800 Subject: [PATCH] ext4: fix off-by-one errors in fast-commit block filling
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@vger.kernel.org # v5.10+ Signed-off-by: Eric Biggers ebiggers@google.com Link: https://lore.kernel.org/r/20221106224841.279231-7-ebiggers@kernel.org Signed-off-by: Theodore Ts'o tytso@mit.edu
diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c index 892fa7c7a768..7ed71c652f67 100644 --- a/fs/ext4/fast_commit.c +++ b/fs/ext4/fast_commit.c @@ -714,43 +714,43 @@ static u8 *ext4_fc_reserve_space(struct super_block *sb, int len, u32 *crc) 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);
@@ -758,7 +758,7 @@ static u8 *ext4_fc_reserve_space(struct super_block *sb, int len, u32 *crc) 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; }
@@ -789,7 +789,7 @@ static int ext4_fc_write_tail(struct super_block *sb, u32 crc) 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); @@ -2056,7 +2056,7 @@ static int ext4_fc_replay_scan(journal_t *journal, 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; @@ -2077,7 +2077,7 @@ static int ext4_fc_replay_scan(journal_t *journal, }
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; @@ -2195,9 +2195,9 @@ static int ext4_fc_replay(journal_t *journal, struct buffer_head *bh, #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;