Messages in this thread Patch in this message | | | Date | Thu, 5 Nov 2009 09:38:21 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: CVE-2009-2584 |
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On Thu, 5 Nov 2009, Linus Torvalds wrote: > > Untested, of course. And since almost nobody has the hardware, so it's not > like it's ever likely to _be_ tested. > > Linus > > --- > drivers/misc/sgi-gru/gruprocfs.c | 4 +++- > 1 files changed, 3 insertions(+), 1 deletions(-) > > diff --git a/drivers/misc/sgi-gru/gruprocfs.c b/drivers/misc/sgi-gru/gruprocfs.c > index ccd4408..c0e17b0 100644 > --- a/drivers/misc/sgi-gru/gruprocfs.c > +++ b/drivers/misc/sgi-gru/gruprocfs.c > @@ -164,7 +164,9 @@ static ssize_t options_write(struct file *file, const char __user *userbuf, > unsigned long val; > char buf[80]; > > - if (strncpy_from_user(buf, userbuf, sizeof(buf) - 1) < 0) > + if (count >= sizeof(buf)) > + count = sizeof(buf)-1; > + if (copy_from_user(buf, userbuf, count)) > return -EFAULT; > buf[count - 1] = '\0';
And it's wrong. That 'count-1' was always wrong. It seems to _depend_ on people doing things like
echo number > /proc/..
and the 'echo' adding a '\n' at the end, and then 'buf[count-1] = 0' clearing away the '\n'.
Which is pointless, since '\n' at the end is the _one_ thing strict_strtoul() accepts. And it's wrong, because it means that
echo -n number > /proc..
fails.
In other words, the whole function is utter sh*t as far as I can tell. There's basically not a single correct line in the whole thing.
Even the 'strict_strtoul()' line is absolute and utter crap, since it forces decimal numbers, but 'options_show()' will then show it as a hex number (and a hex number is natural, since it's a set of flags). It also doesn't actually return an error if you write some invalid value, and it's totally pointless to have that 'val' temporary, since the strict_strtoul function only writes the result if it is successful _anyway_.
The size of the buffer is also insane. Since the _only_ thing we will ever accept is a number, there's no point in allowing all that many characters. And silently ignoring the extra characters kind of makes the whole 'strict' part of 'strict_strtoul()' pointless.
So here's a second try. I guess the 'return count/-EFAULT' lines were actually correct after all. So it wasn't _all_ buggy or insane.
Still entirely untested.
Linus
--- drivers/misc/sgi-gru/gruprocfs.c | 13 +++++++------ 1 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/drivers/misc/sgi-gru/gruprocfs.c b/drivers/misc/sgi-gru/gruprocfs.c index ccd4408..762f179 100644 --- a/drivers/misc/sgi-gru/gruprocfs.c +++ b/drivers/misc/sgi-gru/gruprocfs.c @@ -161,14 +161,15 @@ static int options_show(struct seq_file *s, void *p) static ssize_t options_write(struct file *file, const char __user *userbuf, size_t count, loff_t *data) { - unsigned long val; - char buf[80]; + char buf[16]; - if (strncpy_from_user(buf, userbuf, sizeof(buf) - 1) < 0) + if (count >= sizeof(buf)) + return -EINVAL; + if (copy_from_user(buf, userbuf, count)) return -EFAULT; - buf[count - 1] = '\0'; - if (!strict_strtoul(buf, 10, &val)) - gru_options = val; + buf[count] = '\0'; + if (strict_strtoul(buf, 0, &gru_options)) + return -EINVAL; return count; }
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