diff options
| author | Robert Richter <robert.richter@amd.com> | 2011-12-19 16:38:30 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-12-19 17:18:43 +0100 |
| commit | 913050b91eb94f194392dd797b1ff3779f606ac0 (patch) | |
| tree | bcb861e17dc40875ef0f694641392b7177f04852 /drivers/oprofile | |
| parent | 497f16f21a04060098c0da6ed522fbcafb90c0db (diff) | |
| download | lwn-913050b91eb94f194392dd797b1ff3779f606ac0.tar.gz lwn-913050b91eb94f194392dd797b1ff3779f606ac0.zip | |
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>
Diffstat (limited to 'drivers/oprofile')
| -rw-r--r-- | drivers/oprofile/oprofile_files.c | 7 | ||||
| -rw-r--r-- | drivers/oprofile/oprofilefs.c | 11 |
2 files changed, 13 insertions, 5 deletions
diff --git a/drivers/oprofile/oprofile_files.c b/drivers/oprofile/oprofile_files.c index 89f63456646f..84a208dbed93 100644 --- a/drivers/oprofile/oprofile_files.c +++ b/drivers/oprofile/oprofile_files.c @@ -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 diff --git a/drivers/oprofile/oprofilefs.c b/drivers/oprofile/oprofilefs.c index d0de6cc2d7a5..2f0aa0f700e6 100644 --- a/drivers/oprofile/oprofilefs.c +++ b/drivers/oprofile/oprofilefs.c @@ -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); |