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[PATCH 2/6] x86/ras/mce_amd_inj: Return early on invalid input

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From: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>

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@amd.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: http://lkml.kernel.org/r/1443190851-2172-2-git-send-email-Aravind.Gopalakrishnan@amd.com
Signed-off-by: Borislav Petkov <bp@suse.de>
---
 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 17e35b5bf779..4fd8bb9b90b9 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 = {
-- 
2.3.5

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[PATCH 0/6] tip-queue 2015-10-12 Borislav Petkov <bp@alien8.de> - 2015-10-12 11:30 +0200
  [PATCH 3/6] x86/ras/mce_amd_inj: Trigger deferred and thresholding errors interrupts Borislav Petkov <bp@alien8.de> - 2015-10-12 11:30 +0200
    [tip:ras/core] x86/ras/mce_amd_inj:   Trigger deferred and thresholding errors interrupts tip-bot for Aravind Gopalakrishnan <tipbot@zytor.com> - 2015-10-12 16:40 +0200
  [PATCH 2/6] x86/ras/mce_amd_inj: Return early on invalid input Borislav Petkov <bp@alien8.de> - 2015-10-12 11:30 +0200
    [tip:ras/core] x86/ras/mce_amd_inj: Return early on invalid input tip-bot for Aravind Gopalakrishnan <tipbot@zytor.com> - 2015-10-12 16:40 +0200
  [PATCH 4/6] x86/ras/mce_amd_inj: Inject bank 4 errors on the NBC Borislav Petkov <bp@alien8.de> - 2015-10-12 11:30 +0200
    [tip:ras/core] x86/ras/mce_amd_inj:   Inject bank 4 errors on the NBC tip-bot for Aravind Gopalakrishnan <tipbot@zytor.com> - 2015-10-12 16:40 +0200
  [PATCH 6/6] x86/microcode/amd: Do not overwrite final patch levels Borislav Petkov <bp@alien8.de> - 2015-10-12 11:30 +0200
    [tip:ras/core] x86/microcode/amd:   Do not overwrite final patch levels tip-bot for Borislav Petkov <tipbot@zytor.com> - 2015-10-12 16:40 +0200

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