powerpc/vdso: Fix VDSO data access when running in a non-root time na…

…mespace When running in a non-root time namespace, the global VDSO data page is replaced by a dedicated namespace data page and the global data page is mapped next to it. Detailed explanations can be found at commit 660fd04 ("lib/vdso: Prepare for time namespace support"). When it happens, __kernel_get_syscall_map and __kernel_get_tbfreq and __kernel_sync_dicache don't work anymore because they read 0 instead of the data they need. To address that, clock_mode has to be read. When it is set to VDSO_CLOCKMODE_TIMENS, it means it is a dedicated namespace data page and the global data is located on the following page. Add a macro called get_realdatapage which reads clock_mode and add PAGE_SIZE to the pointer provided by get_datapage macro when clock_mode is equal to VDSO_CLOCKMODE_TIMENS. Use this new macro instead of get_datapage macro except for time functions as they handle it internally. Fixes: 74205b3 ("powerpc/vdso: Add support for time namespaces") Reported-by: Jason A. Donenfeld <[email protected]> Closes: https://lore.kernel.org/all/[email protected]/ Signed-off-by: Christophe Leroy <[email protected]> Acked-by: Michael Ellerman <[email protected]> Signed-off-by: Jason A. Donenfeld <[email protected]>
mj22226 · Sep 13, 2024 · c730493 · c730493
1 parent 8bc7c5e
commit c730493
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Showing 4 changed files with 20 additions and 3 deletions.
diff --git a/arch/powerpc/include/asm/vdso_datapage.h b/arch/powerpc/include/asm/vdso_datapage.h
@@ -111,6 +111,21 @@ extern struct vdso_arch_data *vdso_data;
 	addi	\ptr, \ptr, (_vdso_datapage - 999b)@l
 .endm
 
+#include <asm/asm-offsets.h>
+#include <asm/page.h>
+
+.macro get_realdatapage ptr scratch
+	get_datapage \ptr
+#ifdef CONFIG_TIME_NS
+	lwz	\scratch, VDSO_CLOCKMODE_OFFSET(\ptr)
+	xoris	\scratch, \scratch, VDSO_CLOCKMODE_TIMENS@h
+	xori	\scratch, \scratch, VDSO_CLOCKMODE_TIMENS@l
+	cntlzw	\scratch, \scratch
+	rlwinm	\scratch, \scratch, PAGE_SHIFT - 5, 1 << PAGE_SHIFT
+	add	\ptr, \ptr, \scratch
+#endif
+.endm
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* __KERNEL__ */

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
@@ -346,6 +346,8 @@ int main(void)
 #else
 	OFFSET(CFG_SYSCALL_MAP32, vdso_arch_data, syscall_map);
 #endif
+	OFFSET(VDSO_CLOCKMODE_OFFSET, vdso_arch_data, data[0].clock_mode);
+	DEFINE(VDSO_CLOCKMODE_TIMENS, VDSO_CLOCKMODE_TIMENS);
 
 #ifdef CONFIG_BUG
 	DEFINE(BUG_ENTRY_SIZE, sizeof(struct bug_entry));

diff --git a/arch/powerpc/kernel/vdso/cacheflush.S b/arch/powerpc/kernel/vdso/cacheflush.S
@@ -30,7 +30,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
 #ifdef CONFIG_PPC64
 	mflr	r12
   .cfi_register lr,r12
-	get_datapage	r10
+	get_realdatapage	r10, r11
 	mtlr	r12
   .cfi_restore	lr
 #endif

diff --git a/arch/powerpc/kernel/vdso/datapage.S b/arch/powerpc/kernel/vdso/datapage.S
@@ -28,7 +28,7 @@ V_FUNCTION_BEGIN(__kernel_get_syscall_map)
 	mflr	r12
   .cfi_register lr,r12
 	mr.	r4,r3
-	get_datapage	r3
+	get_realdatapage	r3, r11
 	mtlr	r12
 #ifdef __powerpc64__
 	addi	r3,r3,CFG_SYSCALL_MAP64
@@ -52,7 +52,7 @@ V_FUNCTION_BEGIN(__kernel_get_tbfreq)
   .cfi_startproc
 	mflr	r12
   .cfi_register lr,r12
-	get_datapage	r3
+	get_realdatapage	r3, r11
 #ifndef __powerpc64__
 	lwz	r4,(CFG_TB_TICKS_PER_SEC + 4)(r3)
 #endif