linux-kernel - [PATCH v2] MIPS: kernel: Fix random segmentation faults

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Message-ID: <20251120121030.28524-1-tsbogend@alpha.franken.de>
Date: Thu, 20 Nov 2025 13:10:29 +0100
From: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nam Cao <namcao@...utronix.de>,
	linux-mips@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] MIPS: kernel: Fix random segmentation faults

Commit 69896119dc9d ("MIPS: vdso: Switch to generic storage
implementation") switches to a generic vdso storage, which increases
the number of data pages from 1 to 4. But there is only one page
reserved, which causes segementation faults depending where the VDSO
area is randomized to. To fix this use the same size of reservation
and allocation of the VDSO data pages.

Fixes: 69896119dc9d ("MIPS: vdso: Switch to generic storage implementation")
Signed-off-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
---
v2: Don't reserve additionnal VDSO_NR_PAGES, but reserve VDSO_NR_PAGES
    instead of the one page before.
    Reworked description
v1: https://lore.kernel.org/all/20251117191815.69556-1-tsbogend@alpha.franken.de/

 arch/mips/kernel/process.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 29191fa1801e..a3101f2268c6 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -692,7 +692,7 @@ unsigned long mips_stack_top(void)
 	/* Space for the VDSO, data page & GIC user page */
 	if (current->thread.abi) {
 		top -= PAGE_ALIGN(current->thread.abi->vdso->size);
-		top -= PAGE_SIZE;
+		top -= VDSO_NR_PAGES * PAGE_SIZE;
 		top -= mips_gic_present() ? PAGE_SIZE : 0;
 
 		/* Space to randomize the VDSO base */
-- 
2.43.0