From: Johannes Weiner hannes@cmpxchg.org
mainline inclusion from mainline-v6.12 commit dcf32ea7ecede94796fb30231b3969d7c838374c category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IBC5I1
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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syzbot and Daan report a NULL pointer crash in the new full swap cluster reclaim work:
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] CPU: 1 UID: 0 PID: 51 Comm: kworker/1:1 Not tainted 6.12.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 Workqueue: events swap_reclaim_work RIP: 0010:__list_del_entry_valid_or_report+0x20/0x1c0 lib/list_debug.c:49 Code: 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 89 fe 48 83 c7 08 48 83 ec 18 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 19 01 00 00 48 89 f2 48 8b 4e 08 48 b8 00 00 00 RSP: 0018:ffffc90000bb7c30 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff88807b9ae078 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000008 RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: 000000000000004f R12: dffffc0000000000 R13: ffffffffffffffb8 R14: ffff88807b9ae000 R15: ffffc90003af1000 FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fffaca68fb8 CR3: 00000000791c8000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace:
<TASK> __list_del_entry_valid include/linux/list.h:124 [inline] __list_del_entry include/linux/list.h:215 [inline] list_move_tail include/linux/list.h:310 [inline] swap_reclaim_full_clusters+0x109/0x460 mm/swapfile.c:748 swap_reclaim_work+0x2e/0x40 mm/swapfile.c:779
The syzbot console output indicates a virtual environment where swapfile is on a rotational device. In this case, clusters aren't actually used, and si->full_clusters is not initialized. Daan's report is from qemu, so likely rotational too.
Make sure to only schedule the cluster reclaim work when clusters are actually in use.
Link: https://lkml.kernel.org/r/20241107142335.GB1172372@cmpxchg.org Link: https://lore.kernel.org/lkml/672ac50b.050a0220.2edce.1517.GAE@google.com/ Link: https://github.com/systemd/systemd/issues/35044 Fixes: 5168a68eb78f ("mm, swap: avoid over reclaim of full clusters") Reported-by: syzbot+078be8bfa863cb9e0c6b@syzkaller.appspotmail.com Signed-off-by: Johannes Weiner hannes@cmpxchg.org Reported-by: Daan De Meyer daan.j.demeyer@gmail.com Cc: Kairui Song ryncsn@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Liu Shixin liushixin2@huawei.com --- mm/swapfile.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c index 6f3cbf3a2f0d..3b48159820f2 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -921,7 +921,7 @@ static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset, si->highest_bit = 0; del_from_avail_list(si);
- if (vm_swap_full()) + if (si->cluster_info && vm_swap_full()) schedule_work(&si->reclaim_work); } }