[PATCH] codetag: debug: mark codetags for poisoned page as empty

[Hao Ge <hao.ge@linux.dev>]

From: Hao Ge <gehao@kylinos.cn>

The PG_hwpoison page will be caught and isolated on the entrance to
the free buddy page pool.

But for poisoned pages which software injected errors,
we can reclaim it through unpoison_memory.

So mark codetags for it as empty,just like when a page
is first added to the buddy system.

It was detected by [1] and the following WARN occurred:

[  113.930443][ T3282] ------------[ cut here ]------------
[  113.931105][ T3282] alloc_tag was not set
[  113.931576][ T3282] WARNING: CPU: 2 PID: 3282 at ./include/linux/alloc_tag.h:130 pgalloc_tag_sub.part.66+0x154/0x164
[  113.932866][ T3282] Modules linked in: hwpoison_inject fuse ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 xt_conntrack ebtable_nat ebtable_broute ip6table_nat ip6table_man4
[  113.941638][ T3282] CPU: 2 UID: 0 PID: 3282 Comm: madvise11 Kdump: loaded Tainted: G        W          6.11.0-rc4-dirty #18
[  113.943003][ T3282] Tainted: [W]=WARN
[  113.943453][ T3282] Hardware name: QEMU KVM Virtual Machine, BIOS unknown 2/2/2022
[  113.944378][ T3282] pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[  113.945319][ T3282] pc : pgalloc_tag_sub.part.66+0x154/0x164
[  113.946016][ T3282] lr : pgalloc_tag_sub.part.66+0x154/0x164
[  113.946706][ T3282] sp : ffff800087093a10
[  113.947197][ T3282] x29: ffff800087093a10 x28: ffff0000d7a9d400 x27: ffff80008249f0a0
[  113.948165][ T3282] x26: 0000000000000000 x25: ffff80008249f2b0 x24: 0000000000000000
[  113.949134][ T3282] x23: 0000000000000001 x22: 0000000000000001 x21: 0000000000000000
[  113.950597][ T3282] x20: ffff0000c08fcad8 x19: ffff80008251e000 x18: ffffffffffffffff
[  113.952207][ T3282] x17: 0000000000000000 x16: 0000000000000000 x15: ffff800081746210
[  113.953161][ T3282] x14: 0000000000000000 x13: 205d323832335420 x12: 5b5d353031313339
[  113.954120][ T3282] x11: ffff800087093500 x10: 000000000000005d x9 : 00000000ffffffd0
[  113.955078][ T3282] x8 : 7f7f7f7f7f7f7f7f x7 : ffff80008236ba90 x6 : c0000000ffff7fff
[  113.956036][ T3282] x5 : ffff000b34bf4dc8 x4 : ffff8000820aba90 x3 : 0000000000000001
[  113.956994][ T3282] x2 : ffff800ab320f000 x1 : 841d1e35ac932e00 x0 : 0000000000000000
[  113.957962][ T3282] Call trace:
[  113.958350][ T3282]  pgalloc_tag_sub.part.66+0x154/0x164
[  113.959000][ T3282]  pgalloc_tag_sub+0x14/0x1c
[  113.959539][ T3282]  free_unref_page+0xf4/0x4b8
[  113.960096][ T3282]  __folio_put+0xd4/0x120
[  113.960614][ T3282]  folio_put+0x24/0x50
[  113.961103][ T3282]  unpoison_memory+0x4f0/0x5b0
[  113.961678][ T3282]  hwpoison_unpoison+0x30/0x48 [hwpoison_inject]
[  113.962436][ T3282]  simple_attr_write_xsigned.isra.34+0xec/0x1cc
[  113.963183][ T3282]  simple_attr_write+0x38/0x48
[  113.963750][ T3282]  debugfs_attr_write+0x54/0x80
[  113.964330][ T3282]  full_proxy_write+0x68/0x98
[  113.964880][ T3282]  vfs_write+0xdc/0x4d0
[  113.965372][ T3282]  ksys_write+0x78/0x100
[  113.965875][ T3282]  __arm64_sys_write+0x24/0x30
[  113.966440][ T3282]  invoke_syscall+0x7c/0x104
[  113.966984][ T3282]  el0_svc_common.constprop.1+0x88/0x104
[  113.967652][ T3282]  do_el0_svc+0x2c/0x38
[  113.968893][ T3282]  el0_svc+0x3c/0x1b8
[  113.969379][ T3282]  el0t_64_sync_handler+0x98/0xbc
[  113.969980][ T3282]  el0t_64_sync+0x19c/0x1a0
[  113.970511][ T3282] ---[ end trace 0000000000000000 ]---

Link [1]: https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/madvise/madvise11.c

Fixes: a8fc28dad6d5 ("alloc_tag: introduce clear_page_tag_ref() helper function")
Cc: stable@vger.kernel.org # v6.10
Signed-off-by: Hao Ge <gehao@kylinos.cn>
---
 mm/page_alloc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c565de8f48e9..7ccd2157d092 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1054,6 +1054,14 @@ __always_inline bool free_pages_prepare(struct page *page,
 		reset_page_owner(page, order);
 		page_table_check_free(page, order);
 		pgalloc_tag_sub(page, 1 << order);
+
+		/*
+		 * For poisoned pages which software injected errors,
+		 * we can reclaim it through unpoison_memory.
+		 * so mark codetags for it as empty,
+		 * just like when a page is first added to the buddy system.
+		 */
+		clear_page_tag_ref(page);
 		return false;
 	}
 
-- 
2.25.1