dm-integrity: Avoid divide by zero in table status in Inline mode

In Inline mode, the journal is unused, and journal_sectors is zero.

Calculating the journal watermark requires dividing by journal_sectors,
which should be done only if the journal is configured.

Otherwise, a simple table query (dmsetup table) can cause OOPS.

This bug did not show on some systems, perhaps only due to
compiler optimization.

On my 32-bit testing machine, this reliably crashes with the following:

 : Oops: divide error: 0000 [#1] PREEMPT SMP
 : CPU: 0 UID: 0 PID: 2450 Comm: dmsetup Not tainted 6.14.0-rc2+ #959
 : EIP: dm_integrity_status+0x2f8/0xab0 [dm_integrity]
 ...

Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: fb0987682c62 ("dm-integrity: introduce the Inline mode")
Cc: stable@vger.kernel.org # 6.11+

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index ee9f7cecd78e0e796caa5c4bcfc186262ecb2068..555dc06b94228775de79fabdebe2705e258183a0 100644 (file)
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -3790,10 +3790,6 @@ static void dm_integrity_status(struct dm_target *ti, status_type_t type,
                break;
 
        case STATUSTYPE_TABLE: {
-               __u64 watermark_percentage = (__u64)(ic->journal_entries - ic->free_sectors_threshold) * 100;
-
-               watermark_percentage += ic->journal_entries / 2;
-               do_div(watermark_percentage, ic->journal_entries);
                arg_count = 3;
                arg_count += !!ic->meta_dev;
                arg_count += ic->sectors_per_block != 1;
@@ -3826,6 +3822,10 @@ static void dm_integrity_status(struct dm_target *ti, status_type_t type,
                DMEMIT(" interleave_sectors:%u", 1U << ic->sb->log2_interleave_sectors);
                DMEMIT(" buffer_sectors:%u", 1U << ic->log2_buffer_sectors);
                if (ic->mode == 'J') {
+                       __u64 watermark_percentage = (__u64)(ic->journal_entries - ic->free_sectors_threshold) * 100;
+
+                       watermark_percentage += ic->journal_entries / 2;
+                       do_div(watermark_percentage, ic->journal_entries);
                        DMEMIT(" journal_watermark:%u", (unsigned int)watermark_percentage);
                        DMEMIT(" commit_time:%u", ic->autocommit_msec);
                }