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Mon, 17 Aug 2026 03:06:08 -0700 (PDT) Received: from localhost.localdomain ([175.159.181.20]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3954d3b3b91sm1767284a91.13.2026.08.17.03.06.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Aug 2026 03:06:08 -0700 (PDT) From: Yu Junzhe To: Mike Snitzer , Mikulas Patocka , Benjamin Marzinski , Alasdair Kergon Cc: dm-devel@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [BUG] dm-integrity: mode R resume NULL deref when DIRTY_BITMAP is set Date: Mon, 17 Aug 2026 10:06:04 +0000 Message-ID: <20260817100605.292-1-junzheyu1@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Hello, I am reporting a null-pointer dereference in dm-integrity resume: recovery mode R skips journal allocation, but dm_integrity_resume() still issues journal I/O when the on-disk superblock has SB_FLAG_DIRTY_BITMAP. Summary ======= create_journal() runs only when mode != 'R', so ic->journal stays NULL. Resume treats DIRTY_BITMAP as "journal pages hold a bitmap" and calls rw_journal_sectors() before any journal/mode check: if (ic->sb->flags & cpu_to_le32(SB_FLAG_DIRTY_BITMAP)) { rw_journal_sectors(ic, REQ_OP_READ, ...); /* uses ic->journal[] */ rw_journal_sectors() then passes that NULL page list into dm_io(): io_req.mem.type = DM_IO_PAGE_LIST; io_req.mem.ptr.pl = &ic->journal[pl_index]; /* NULL in mode R */ list_get_page() does *p = pl->page with pl == NULL (KASAN range [0x8-0xf]). DIRTY_BITMAP is set while bitmap mode (B) is active and is cleared on a clean postsuspend. It remains on disk after an unclean stop of mode B (crash / power loss). Reloading that device in recovery mode R is a documented recovery path and hits this bug. Affected ======== - Confirmed on Linux 6.6.144 (da47cbc254661aa66d61ef061485a7080305c4be), KASAN guest - Still present on torvalds/linux master as of 2026-08-17: resume still calls rw_journal_sectors() under DIRTY_BITMAP with no journal / mode-R guard - Files: drivers/md/dm-integrity.c - Config: CONFIG_DM=y, CONFIG_DM_INTEGRITY=y (KASAN for the report) Crash excerpt (from minimized PoC) ================================== KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] CPU: 0 PID: 234 Comm: repro Not tainted 6.6.144 #15 RIP: 0010:list_get_page+0x7e/0x150 Call Trace: dispatch_io sync_io dm_io rw_journal_sectors dm_integrity_resume dm_table_resume_targets __dm_resume dm_resume dev_suspend ctl_ioctl dm_ctl_ioctl __x64_sys_ioctl Kernel panic - not syncing: Fatal exception Full oops and a self-contained Docker/QEMU reproducer (poc.c + KASAN guest) are available on request. I am happy to test patches or send the reproducer package. Thanks, Yu Junzhe FuzzAnything