a8e5e5146a
Prior to commit 69e3b846d8a7 ("arm64: mte: Sync tags for pages where PTE
is untagged"), mte_sync_tags() was only called for pte_tagged() entries
(those mapped with PROT_MTE). Therefore mte_sync_tags() could safely use
test_and_set_bit(PG_mte_tagged, &page->flags) without inadvertently
setting PG_mte_tagged on an untagged page.
The above commit was required as guests may enable MTE without any
control at the stage 2 mapping, nor a PROT_MTE mapping in the VMM.
However, the side-effect was that any page with a PTE that looked like
swap (or migration) was getting PG_mte_tagged set automatically. A
subsequent page copy (e.g. migration) copied the tags to the destination
page even if the tags were owned by KASAN.
This issue was masked by the page_kasan_tag_reset() call introduced in
commit e5b8d9218951 ("arm64: mte: reset the page tag in page->flags").
When this commit was reverted (20794545c146), KASAN started reporting
access faults because the overriding tags in a page did not match the
original page->flags (with CONFIG_KASAN_HW_TAGS=y):
BUG: KASAN: invalid-access in copy_page+0x10/0xd0 arch/arm64/lib/copy_page.S:26
Read at addr f5ff000017f2e000 by task syz-executor.1/2218
Pointer tag: [f5], memory tag: [f2]
Move the PG_mte_tagged bit setting from mte_sync_tags() to the actual
place where tags are cleared (mte_sync_page_tags()) or restored
(mte_restore_tags()).
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: syzbot+c2c79c6d6eddc5262b77@syzkaller.appspotmail.com
Fixes: 69e3b846d8a7 ("arm64: mte: Sync tags for pages where PTE is untagged")
Cc: <stable@vger.kernel.org> # 5.14.x
Cc: Steven Price <steven.price@arm.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/0000000000004387dc05e5888ae5@google.com/
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20221006163354.3194102-1-catalin.marinas@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
89 lines
1.9 KiB
C
89 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/pagemap.h>
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#include <linux/xarray.h>
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#include <linux/slab.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <asm/mte.h>
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static DEFINE_XARRAY(mte_pages);
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void *mte_allocate_tag_storage(void)
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{
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/* tags granule is 16 bytes, 2 tags stored per byte */
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return kmalloc(MTE_PAGE_TAG_STORAGE, GFP_KERNEL);
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}
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void mte_free_tag_storage(char *storage)
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{
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kfree(storage);
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}
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int mte_save_tags(struct page *page)
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{
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void *tag_storage, *ret;
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if (!test_bit(PG_mte_tagged, &page->flags))
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return 0;
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tag_storage = mte_allocate_tag_storage();
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if (!tag_storage)
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return -ENOMEM;
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mte_save_page_tags(page_address(page), tag_storage);
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/* page_private contains the swap entry.val set in do_swap_page */
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ret = xa_store(&mte_pages, page_private(page), tag_storage, GFP_KERNEL);
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if (WARN(xa_is_err(ret), "Failed to store MTE tags")) {
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mte_free_tag_storage(tag_storage);
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return xa_err(ret);
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} else if (ret) {
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/* Entry is being replaced, free the old entry */
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mte_free_tag_storage(ret);
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}
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return 0;
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}
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bool mte_restore_tags(swp_entry_t entry, struct page *page)
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{
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void *tags = xa_load(&mte_pages, entry.val);
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if (!tags)
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return false;
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/*
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* Test PG_mte_tagged again in case it was racing with another
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* set_pte_at().
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*/
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if (!test_and_set_bit(PG_mte_tagged, &page->flags))
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mte_restore_page_tags(page_address(page), tags);
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return true;
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}
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void mte_invalidate_tags(int type, pgoff_t offset)
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{
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swp_entry_t entry = swp_entry(type, offset);
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void *tags = xa_erase(&mte_pages, entry.val);
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mte_free_tag_storage(tags);
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}
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void mte_invalidate_tags_area(int type)
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{
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swp_entry_t entry = swp_entry(type, 0);
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swp_entry_t last_entry = swp_entry(type + 1, 0);
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void *tags;
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XA_STATE(xa_state, &mte_pages, entry.val);
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xa_lock(&mte_pages);
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xas_for_each(&xa_state, tags, last_entry.val - 1) {
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__xa_erase(&mte_pages, xa_state.xa_index);
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mte_free_tag_storage(tags);
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}
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xa_unlock(&mte_pages);
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}
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