[PATCH RFC v2 24/27] arm64: mte: Handle fatal signal in reserve_tag_storage()
From: Alexandru Elisei <hidden>
Date: 2023-11-19 16:59:46
Also in:
kvmarm, linux-arch, linux-fsdevel, linux-mm, linux-trace-kernel, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
As long as a fatal signal is pending, alloc_contig_range() will fail with -EINTR. This makes it impossible for tag storage allocation to succeed, and the page allocator will print an OOM splat. The process is going to be killed, so return 0 (success) from reserve_tag_storage() to allow the page allocator to make progress. set_pte_at() will map it with PAGE_FAULT_ON_ACCESS and subsequent accesses from different threads will cause a fault until the signal is delivered. Signed-off-by: Alexandru Elisei <redacted> --- arch/arm64/kernel/mte_tag_storage.c | 17 +++++++++++++++++ arch/arm64/mm/fault.c | 5 +++++ 2 files changed, 22 insertions(+)
diff --git a/arch/arm64/kernel/mte_tag_storage.c b/arch/arm64/kernel/mte_tag_storage.c
index 6b11bb408b51..602fdc70db1c 100644
--- a/arch/arm64/kernel/mte_tag_storage.c
+++ b/arch/arm64/kernel/mte_tag_storage.c@@ -572,6 +572,23 @@ int reserve_tag_storage(struct page *page, int order, gfp_t gfp) break; } + /* + * alloc_contig_range() returns -EINTR from + * __alloc_contig_migrate_range() if a fatal signal is pending. + * As long as the signal hasn't been handled, it is impossible + * to reserve tag storage for any page. Stop trying to reserve + * tag storage, but return 0 so the page allocator can make + * forward progress, instead of printing an OOM splat. + * + * The tagged page with missing tag storage will be mapped with + * PAGE_FAULT_ON_ACCESS in set_pte_at(), which means accesses + * until the signal is delivered will cause a fault. + */ + if (ret == -EINTR) { + ret = 0; + goto out_error; + } + if (ret) goto out_error;
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 964c5ae161a3..fdc98c5828bf 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c@@ -950,6 +950,11 @@ gfp_t arch_calc_vma_gfp(struct vm_area_struct *vma, gfp_t gfp) void tag_clear_highpage(struct page *page) { + if (tag_storage_enabled() && unlikely(!page_tag_storage_reserved(page))) { + clear_page(page_address(page)); + return; + } + /* Newly allocated page, shouldn't have been tagged yet */ WARN_ON_ONCE(!try_page_mte_tagging(page)); mte_zero_clear_page_tags(page_address(page));
--
2.42.1
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