This is a note to let you know that I've just added the patch titled
powerpc/vdso: Fix VDSO data access when running in a non-root time namespace
to the 6.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-vdso-fix-vdso-data-access-when-running-in-a-.patch
and it can be found in the queue-6.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 929d5cd7458d50c8de5b59b7e56d379a7852a96c
Author: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Date: Fri Sep 6 10:33:43 2024 +0200
powerpc/vdso: Fix VDSO data access when running in a non-root time namespace
[ Upstream commit c73049389e58c01e2e3bbfae900c8daeee177191 ]
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 660fd04f9317 ("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: 74205b3fc2ef ("powerpc/vdso: Add support for time namespaces")
Reported-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Closes: https://lore.kernel.org/all/ZtnYqZI-nrsNslwy@xxxxxxxxx/
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Acked-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/powerpc/include/asm/vdso_datapage.h b/arch/powerpc/include/asm/vdso_datapage.h
index a585c8e538ff0..939daf6b695ef 100644
--- 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
index f029755f9e69a..0c5c0fbf62417 100644
--- 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
index 0085ae464dac9..3b2479bd2f9a1 100644
--- 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
index db8e167f01667..2b19b6201a33a 100644
--- 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
