From a70f9fe52daa839d3925ac7e2dbd0ca758434493 Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Mon, 4 Jan 2016 15:55:10 +1100 Subject: [PATCH] xfs: detect and handle invalid iclog size set by mkfs XFS log records have separate fields for the record size and the iclog size used to write the record. mkfs.xfs zeroes the log and writes an unmount record to generate a clean log for the subsequent mount. The userspace record logging code has a bug where the iclog size (h_size) field of the log record is hardcoded to 32k, even if a log stripe unit is specified. The log record length is correctly extended to the stripe unit. Since the kernel log recovery code uses the h_size field to determine the log buffer size, this means that the kernel can attempt to read/process records larger than the buffer size and overrun the buffer. This has historically not been a problem because the kernel doesn't actually run through log recovery in the clean unmount case. Instead, the kernel detects that a single unmount record exists between the head and tail and pushes the tail forward such that the log is viewed as clean (head == tail). Once CRC verification is enabled, however, all records at the head of the log are verified for CRC errors and thus we are susceptible to overrun problems if the iclog field is not correct. While the core problem must be fixed in userspace, this is historical behavior that must be detected in the kernel to avoid severe side effects such as memory corruption and crashes. Update the log buffer size calculation code to detect this condition, warn the user and resize the log buffer based on the log stripe unit. Return a corruption error in cases where this does not look like a clean filesystem (i.e., the log record header indicates more than one operation). Signed-off-by: Brian Foster Reviewed-by: Dave Chinner Signed-off-by: Dave Chinner --- fs/xfs/xfs_log_recover.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c index c5ecaacdd218..4f880d6cfb93 100644 --- a/fs/xfs/xfs_log_recover.c +++ b/fs/xfs/xfs_log_recover.c @@ -4245,7 +4245,7 @@ xlog_do_recovery_pass( xfs_daddr_t blk_no; char *offset; xfs_buf_t *hbp, *dbp; - int error = 0, h_size; + int error = 0, h_size, h_len; int bblks, split_bblks; int hblks, split_hblks, wrapped_hblks; struct hlist_head rhash[XLOG_RHASH_SIZE]; @@ -4274,7 +4274,31 @@ xlog_do_recovery_pass( error = xlog_valid_rec_header(log, rhead, tail_blk); if (error) goto bread_err1; + + /* + * xfsprogs has a bug where record length is based on lsunit but + * h_size (iclog size) is hardcoded to 32k. Now that we + * unconditionally CRC verify the unmount record, this means the + * log buffer can be too small for the record and cause an + * overrun. + * + * Detect this condition here. Use lsunit for the buffer size as + * long as this looks like the mkfs case. Otherwise, return an + * error to avoid a buffer overrun. + */ h_size = be32_to_cpu(rhead->h_size); + h_len = be32_to_cpu(rhead->h_len); + if (h_len > h_size) { + if (h_len <= log->l_mp->m_logbsize && + be32_to_cpu(rhead->h_num_logops) == 1) { + xfs_warn(log->l_mp, + "invalid iclog size (%d bytes), using lsunit (%d bytes)", + h_size, log->l_mp->m_logbsize); + h_size = log->l_mp->m_logbsize; + } else + return -EFSCORRUPTED; + } + if ((be32_to_cpu(rhead->h_version) & XLOG_VERSION_2) && (h_size > XLOG_HEADER_CYCLE_SIZE)) { hblks = h_size / XLOG_HEADER_CYCLE_SIZE; -- 2.20.1