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[v4,1/2] arm64: mm: purge lazily unmapped vm regions before changing permissions

Message ID 20181107103620.16054-2-ard.biesheuvel@linaro.org (mailing list archive)
State New, archived
Headers show
Series get rid of writable linear aliases of read-only vmalloc mappings | expand

Commit Message

Ard Biesheuvel Nov. 7, 2018, 10:36 a.m. UTC 
Call vm_unmap_aliases() every time we apply any changes to permission
attributes of mappings in the vmalloc region. This avoids any potential
issues resulting from lingering writable or executable aliases of
mappings that should be read-only or non-executable, respectively.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 arch/arm64/mm/pageattr.c | 6 ++++++
 1 file changed, 6 insertions(+)
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Patch

diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index a56359373d8b..787f9e385e6d 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -93,6 +93,12 @@  static int change_memory_common(unsigned long addr, int numpages,
 	if (!numpages)
 		return 0;
 
+	/*
+	 * Get rid of potentially aliasing lazily unmapped vm areas that may
+	 * have permissions set that deviate from the ones we are setting here.
+	 */
+	vm_unmap_aliases();
+
 	return __change_memory_common(start, size, set_mask, clear_mask);
 }