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

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[ 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 660fd04f93 ("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: 74205b3fc2 ("powerpc/vdso: Add support for time namespaces")
Reported-by: Jason A. Donenfeld <Jason@zx2c4.com>
Closes: https://lore.kernel.org/all/ZtnYqZI-nrsNslwy@zx2c4.com/
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Christophe Leroy 2024-09-06 10:33:43 +02:00 committed by Greg Kroah-Hartman
parent eba34000e7
commit 3c9f0c9d59
4 changed files with 20 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
arch/powerpc/include/asm/vdso_datapage.h
View File

@ -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__ */

2
arch/powerpc/kernel/asm-offsets.c
View File

@ -347,6 +347,8 @@ 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));

2
arch/powerpc/kernel/vdso/cacheflush.S
View File

@ -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

4
arch/powerpc/kernel/vdso/datapage.S
View File

@ -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