Commit 7fb39882 authored by Milan Broz's avatar Milan Broz Committed by Mikulas Patocka
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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: default avatarMilan Broz <gmazyland@gmail.com>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Fixes: fb098768 ("dm-integrity: introduce the Inline mode")
Cc: stable@vger.kernel.org # 6.11+
parent 0ad2507d

drivers/md/dm-integrity.c

+4 −4
Original line number Diff line number Diff line
@@ -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);

		}