linux-kernel - [tip: x86/sev] x86/insn-eval: Make 0 a valid RIP for insn_get_effective

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Date:   Tue, 15 Jun 2021 10:51:57 -0000
From:   "tip-bot2 for Joerg Roedel" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Joerg Roedel <jroedel@...e.de>, Borislav Petkov <bp@...e.de>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/sev] x86/insn-eval: Make 0 a valid RIP for insn_get_effective_ip()

The following commit has been merged into the x86/sev branch of tip:

Commit-ID:     f2df15639e44d23bf82a86a03092472c7278cd39
Gitweb:        https://git.kernel.org/tip/f2df15639e44d23bf82a86a03092472c7278cd39
Author:        Joerg Roedel <jroedel@...e.de>
AuthorDate:    Wed, 19 May 2021 15:52:49 +02:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Tue, 15 Jun 2021 11:24:21 +02:00

x86/insn-eval: Make 0 a valid RIP for insn_get_effective_ip()

In theory, 0 is a valid value for the instruction pointer so don't use
it as the error return value from insn_get_effective_ip().

Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20210614135327.9921-5-joro@8bytes.org
---
 arch/x86/lib/insn-eval.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index a67afd7..4eecb9c 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -1417,7 +1417,7 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
 	}
 }
 
-static unsigned long insn_get_effective_ip(struct pt_regs *regs)
+static int insn_get_effective_ip(struct pt_regs *regs, unsigned long *ip)
 {
 	unsigned long seg_base = 0;
 
@@ -1430,10 +1430,12 @@ static unsigned long insn_get_effective_ip(struct pt_regs *regs)
 	if (!user_64bit_mode(regs)) {
 		seg_base = insn_get_seg_base(regs, INAT_SEG_REG_CS);
 		if (seg_base == -1L)
-			return 0;
+			return -EINVAL;
 	}
 
-	return seg_base + regs->ip;
+	*ip = seg_base + regs->ip;
+
+	return 0;
 }
 
 /**
@@ -1455,8 +1457,7 @@ int insn_fetch_from_user(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE])
 	unsigned long ip;
 	int not_copied;
 
-	ip = insn_get_effective_ip(regs);
-	if (!ip)
+	if (insn_get_effective_ip(regs, &ip))
 		return 0;
 
 	not_copied = copy_from_user(buf, (void __user *)ip, MAX_INSN_SIZE);
@@ -1484,8 +1485,7 @@ int insn_fetch_from_user_inatomic(struct pt_regs *regs, unsigned char buf[MAX_IN
 	unsigned long ip;
 	int not_copied;
 
-	ip = insn_get_effective_ip(regs);
-	if (!ip)
+	if (insn_get_effective_ip(regs, &ip))
 		return 0;
 
 	not_copied = __copy_from_user_inatomic(buf, (void __user *)ip, MAX_INSN_SIZE);