From: Heiko Carstens Date: Fri, 13 Jun 2025 15:53:04 +0000 (+0200) Subject: s390/ptrace: Fix pointer dereferencing in regs_get_kernel_stack_nth() X-Git-Tag: v6.16-rc4~21^2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7f8073cfb04a97842fe891ca50dad60afd1e3121;p=thirdparty%2Fkernel%2Flinux.git s390/ptrace: Fix pointer dereferencing in regs_get_kernel_stack_nth() The recent change which added READ_ONCE_NOCHECK() to read the nth entry from the kernel stack incorrectly dropped dereferencing of the stack pointer in order to read the requested entry. In result the address of the entry is returned instead of its content. Dereference the pointer again to fix this. Reported-by: Will Deacon Closes: https://lore.kernel.org/r/20250612163331.GA13384@willie-the-truck Fixes: d93a855c31b7 ("s390/ptrace: Avoid KASAN false positives in regs_get_kernel_stack_nth()") Cc: stable@vger.kernel.org Reviewed-by: Alexander Gordeev Signed-off-by: Heiko Carstens Signed-off-by: Alexander Gordeev --- diff --git a/arch/s390/include/asm/ptrace.h b/arch/s390/include/asm/ptrace.h index 62c0ab4a4b9de..0905fa99a31ee 100644 --- a/arch/s390/include/asm/ptrace.h +++ b/arch/s390/include/asm/ptrace.h @@ -265,7 +265,7 @@ static __always_inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *r addr = kernel_stack_pointer(regs) + n * sizeof(long); if (!regs_within_kernel_stack(regs, addr)) return 0; - return READ_ONCE_NOCHECK(addr); + return READ_ONCE_NOCHECK(*(unsigned long *)addr); } /**