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Subject[24/75] oprofile: Fix uninitialized memory access when writing to writing to oprofilefs
3.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Robert Richter <robert.richter@amd.com>

commit 913050b91eb94f194392dd797b1ff3779f606ac0 upstream.

If oprofilefs_ulong_from_user() is called with count equals
zero, *val remains unchanged. Depending on the implementation it
might be uninitialized.

Change oprofilefs_ulong_from_user()'s interface to return count
on success. Thus, we are able to return early if count equals
zero which avoids using *val uninitialized. Fixing all users of
oprofilefs_ulong_ from_user().

This follows write syscall implementation when count is zero:
"If count is zero ... [and if] no errors are detected, 0 will be
returned without causing any other effect." (man 2 write)

Reported-By: Mike Waychison <mikew@google.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: oprofile-list <oprofile-list@lists.sourceforge.net>
Link: http://lkml.kernel.org/r/20111219153830.GH16765@erda.amd.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/s390/oprofile/init.c | 2 +-
drivers/oprofile/oprofile_files.c | 7 ++++---
drivers/oprofile/oprofilefs.c | 11 +++++++++--
3 files changed, 14 insertions(+), 6 deletions(-)

--- a/arch/s390/oprofile/init.c
+++ b/arch/s390/oprofile/init.c
@@ -88,7 +88,7 @@ static ssize_t hwsampler_write(struct fi
return -EINVAL;

retval = oprofilefs_ulong_from_user(&val, buf, count);
- if (retval)
+ if (retval <= 0)
return retval;

if (oprofile_started)
--- a/drivers/oprofile/oprofile_files.c
+++ b/drivers/oprofile/oprofile_files.c
@@ -45,7 +45,7 @@ static ssize_t timeout_write(struct file
return -EINVAL;

retval = oprofilefs_ulong_from_user(&val, buf, count);
- if (retval)
+ if (retval <= 0)
return retval;

retval = oprofile_set_timeout(val);
@@ -84,7 +84,7 @@ static ssize_t depth_write(struct file *
return -EINVAL;

retval = oprofilefs_ulong_from_user(&val, buf, count);
- if (retval)
+ if (retval <= 0)
return retval;

retval = oprofile_set_ulong(&oprofile_backtrace_depth, val);
@@ -141,9 +141,10 @@ static ssize_t enable_write(struct file
return -EINVAL;

retval = oprofilefs_ulong_from_user(&val, buf, count);
- if (retval)
+ if (retval <= 0)
return retval;

+ retval = 0;
if (val)
retval = oprofile_start();
else
--- a/drivers/oprofile/oprofilefs.c
+++ b/drivers/oprofile/oprofilefs.c
@@ -60,6 +60,13 @@ ssize_t oprofilefs_ulong_to_user(unsigne
}


+/*
+ * Note: If oprofilefs_ulong_from_user() returns 0, then *val remains
+ * unchanged and might be uninitialized. This follows write syscall
+ * implementation when count is zero: "If count is zero ... [and if]
+ * no errors are detected, 0 will be returned without causing any
+ * other effect." (man 2 write)
+ */
int oprofilefs_ulong_from_user(unsigned long *val, char const __user *buf, size_t count)
{
char tmpbuf[TMPBUFSIZE];
@@ -79,7 +86,7 @@ int oprofilefs_ulong_from_user(unsigned
spin_lock_irqsave(&oprofilefs_lock, flags);
*val = simple_strtoul(tmpbuf, NULL, 0);
spin_unlock_irqrestore(&oprofilefs_lock, flags);
- return 0;
+ return count;
}


@@ -99,7 +106,7 @@ static ssize_t ulong_write_file(struct f
return -EINVAL;

retval = oprofilefs_ulong_from_user(&value, buf, count);
- if (retval)
+ if (retval <= 0)
return retval;

retval = oprofile_set_ulong(file->private_data, value);



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