From: Ma Wupeng mawupeng1@huawei.com

mainline inclusion from mainline-v6.6-rc1 commit c70699e555537b611f4cb426c26f8ab4a264a8a0 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IB0CMQ CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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Our test finds a WARN_ON in add_to_avail_list. During add_to_avail_list, avail_lists is already in swap_avail_heads, while leads to this WARN_ON.

Here is the simplified calltrace:

------------[ cut here ]------------ Call trace: add_to_avail_list+0xb8/0xc0 swap_range_free+0x110/0x138 swapcache_free_entries+0x100/0x1c0 free_swap_slot+0xbc/0xe0 put_swap_folio+0x1f0/0x2ec delete_from_swap_cache+0x6c/0xd0 folio_free_swap+0xa4/0xe4 __try_to_reclaim_swap+0x9c/0x190 free_swap_and_cache+0x84/0x88 unmap_page_range+0x31c/0x934 unmap_single_vma.isra.0+0x48/0x84 unmap_vmas+0x98/0x10c exit_mmap+0xa4/0x210 mmput+0x88/0x158 do_exit+0x284/0x970 do_group_exit+0x34/0x90 post_copy_siginfo_from_user32+0x0/0x1cc do_notify_resume+0x15c/0x470 el0_svc+0x74/0x84 el0t_64_sync_handler+0xb8/0xbc el0t_64_sync+0x190/0x194

During swapoff, try_to_unuse fails to alloc memory due to memory limit and this leads to the failure of swapoff and causes re-insertion of swap space back into swap_list. During _enable_swap_info, this swap device is added to avail list even this swap device if full. At the same time, one entry in this full swap device in released and we try to add this device into avail list and find it is already in the avail list. This causes this WARN_ON.

To fix this. Don't add to avail list is swap is full.

[akpm@linux-foundation.org: coding-style cleanups] Link: https://lkml.kernel.org/r/20230627120833.2230766-3-mawupeng1@huawei.com Signed-off-by: Ma Wupeng mawupeng1@huawei.com Cc: Hugh Dickins hughd@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Ma Wupeng mawupeng1@huawei.com --- mm/swapfile.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c index b505a827e589..cff30234879d 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2579,7 +2579,10 @@ static void _enable_swap_info(struct swap_info_struct *p) * swap_info_struct. */ plist_add(&p->list, &swap_active_head); - add_to_avail_list(p); + + /* add to available list iff swap device is not full */ + if (p->highest_bit) + add_to_avail_list(p); }

static void enable_swap_info(struct swap_info_struct *p, int prio,