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oprofile: Fix uninitialized memory access when writing to writing to oprofilefs 

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: <stable@vger.kernel.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>
This commit is contained in:
Robert Richter 2011-12-19 16:38:30 +01:00 committed by Ingo Molnar
parent 497f16f21a
commit 913050b91e
3 changed files with 14 additions and 6 deletions
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2
arch/s390/oprofile/init.c
View File

@ -88,7 +88,7 @@ static ssize_t hwsampler_write(struct file *file, char const __user *buf,
return -EINVAL;
retval = oprofilefs_ulong_from_user(&val, buf, count);
if (retval)
if (retval <= 0)
return retval;
if (oprofile_started)

7
drivers/oprofile/oprofile_files.c
View File

@ -45,7 +45,7 @@ static ssize_t timeout_write(struct file *file, char const __user *buf,
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 *file, char const __user *buf, size_t cou
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 *file, char const __user *buf, size_t co
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

11
drivers/oprofile/oprofilefs.c
View File

@ -60,6 +60,13 @@ ssize_t oprofilefs_ulong_to_user(unsigned long val, char __user *buf, size_t cou
}
/*
* 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 long *val, char const __user *buf, size_
raw_spin_lock_irqsave(&oprofilefs_lock, flags);
*val = simple_strtoul(tmpbuf, NULL, 0);
raw_spin_unlock_irqrestore(&oprofilefs_lock, flags);
return 0;
return count;
}
@ -99,7 +106,7 @@ static ssize_t ulong_write_file(struct file *file, char const __user *buf, size_
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);