linux-kernel - [PATCH] ia64: fix ptrace(PTRACE_SYSCALL_INFO

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Message-Id: <20210221002554.333076-2-slyfox@gentoo.org>
Date:   Sun, 21 Feb 2021 00:25:54 +0000
From:   Sergei Trofimovich <slyfox@...too.org>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Cc:     Sergei Trofimovich <slyfox@...too.org>, linux-ia64@...r.kernel.org,
        "Dmitry V . Levin" <ldv@...linux.org>
Subject: [PATCH] ia64: fix ptrace(PTRACE_SYSCALL_INFO_EXIT) sign

In https://bugs.gentoo.org/769614 Dmitry noticed that
`ptrace(PTRACE_GET_SYSCALL_INFO)` does not return error sign properly.

The bug is in mismatch between get/set errors:

static inline long syscall_get_error(struct task_struct *task,
                                     struct pt_regs *regs)
{
        return regs->r10 == -1 ? regs->r8:0;
}

static inline long syscall_get_return_value(struct task_struct *task,
                                            struct pt_regs *regs)
{
        return regs->r8;
}

static inline void syscall_set_return_value(struct task_struct *task,
                                            struct pt_regs *regs,
                                            int error, long val)
{
        if (error) {
                /* error < 0, but ia64 uses > 0 return value */
                regs->r8 = -error;
                regs->r10 = -1;
        } else {
                regs->r8 = val;
                regs->r10 = 0;
        }
}

Tested on v5.10 on rx3600 machine (ia64 9040 CPU).

CC: linux-ia64@...r.kernel.org
CC: linux-kernel@...r.kernel.org
CC: Andrew Morton <akpm@...ux-foundation.org>
Reported-by: Dmitry V. Levin <ldv@...linux.org>
Bug: https://bugs.gentoo.org/769614
Signed-off-by: Sergei Trofimovich <slyfox@...too.org>
---
 arch/ia64/include/asm/syscall.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/ia64/include/asm/syscall.h b/arch/ia64/include/asm/syscall.h
index 6c6f16e409a8..0d23c0049301 100644
--- a/arch/ia64/include/asm/syscall.h
+++ b/arch/ia64/include/asm/syscall.h
@@ -32,7 +32,7 @@ static inline void syscall_rollback(struct task_struct *task,
 static inline long syscall_get_error(struct task_struct *task,
 				     struct pt_regs *regs)
 {
-	return regs->r10 == -1 ? regs->r8:0;
+	return regs->r10 == -1 ? -regs->r8:0;
 }
 
 static inline long syscall_get_return_value(struct task_struct *task,
-- 
2.30.1