linux-kernel - [tip:ras/core] x86/ras/mce_amd_inj: Return early on invalid input

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Date:	Mon, 12 Oct 2015 07:31:03 -0700
From:	tip-bot for Aravind Gopalakrishnan <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, bp@...e.de, tglx@...utronix.de,
	mingo@...nel.org, bp@...en8.de, peterz@...radead.org,
	hpa@...or.com, Aravind.Gopalakrishnan@....com,
	linux-kernel@...r.kernel.org, tony.luck@...el.com
Subject: [tip:ras/core] x86/ras/mce_amd_inj: Return early on invalid input

Commit-ID:  85c9306d44f757d2fb3b0e3e399080a025315c7f
Gitweb:     http://git.kernel.org/tip/85c9306d44f757d2fb3b0e3e399080a025315c7f
Author:     Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
AuthorDate: Mon, 12 Oct 2015 11:22:38 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 12 Oct 2015 16:15:47 +0200

x86/ras/mce_amd_inj: Return early on invalid input

Invalid inputs such as these are currently reported in dmesg as
failing:

  $> echo sweet > flags
  [  122.079139] flags_write: Invalid flags value: et

even though the 'flags' attribute has been updated correctly:

  $> cat flags
  sw

This is because userspace keeps writing the remaining buffer
until it encounters an error.

However, the input as a whole is wrong and we should not be
writing anything to the file. Therefore, correct flags_write()
to return -EINVAL immediately on bad input strings.

Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Borislav Petkov <bp@...en8.de>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Tony Luck <tony.luck@...el.com>
Link: http://lkml.kernel.org/r/1443190851-2172-2-git-send-email-Aravind.Gopalakrishnan@amd.com
Link: http://lkml.kernel.org/r/1444641762-9437-3-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/ras/mce_amd_inj.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/x86/ras/mce_amd_inj.c b/arch/x86/ras/mce_amd_inj.c
index 17e35b5..4fd8bb9 100644
--- a/arch/x86/ras/mce_amd_inj.c
+++ b/arch/x86/ras/mce_amd_inj.c
@@ -129,12 +129,9 @@ static ssize_t flags_write(struct file *filp, const char __user *ubuf,
 {
 	char buf[MAX_FLAG_OPT_SIZE], *__buf;
 	int err;
-	size_t ret;
 
 	if (cnt > MAX_FLAG_OPT_SIZE)
-		cnt = MAX_FLAG_OPT_SIZE;
-
-	ret = cnt;
+		return -EINVAL;
 
 	if (copy_from_user(&buf, ubuf, cnt))
 		return -EFAULT;
@@ -150,9 +147,9 @@ static ssize_t flags_write(struct file *filp, const char __user *ubuf,
 		return err;
 	}
 
-	*ppos += ret;
+	*ppos += cnt;
 
-	return ret;
+	return cnt;
 }
 
 static const struct file_operations flags_fops = {
--
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