Messages in this thread Patch in this message | | | Date | Tue, 5 Jun 2012 16:09:33 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 0/8] Rework KERN_<LEVEL> |
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On Wed, 06 Jun 2012 00:55:00 +0200 Kay Sievers <kay@vrfy.org> wrote:
> On Tue, 2012-06-05 at 14:28 -0700, Andrew Morton wrote: > > > devkmsg_writev() does weird and wonderful things with > > facilities/levels. That function incorrectly returns "success" when > > copy_from_user() faults, btw. > > Oh. Better? > > Thanks, > Kay > > > From: Kay Sievers <kay@vrfy.org> > Subject: kmsg: /dev/kmsg - properly return possible copy_from_user() failure > > Reported-By: Andrew Morton <akpm@linux-foundation.org> > Signed-off-by: Kay Sievers <kay@vrfy.org > --- > printk.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/printk.c b/kernel/printk.c > index 32462d2..6bdacab 100644 > --- a/kernel/printk.c > +++ b/kernel/printk.c > @@ -365,8 +365,10 @@ static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv, > > line = buf; > for (i = 0; i < count; i++) { > - if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) > + if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) { > + ret = -EFAULT; > goto out; > + } > line += iv[i].iov_len; > }
Strictly speaking, when write() encounters an error it should return number-of-bytes-written, or an errno if it wrote zero bytes. So something like
--- a/kernel/printk.c~a +++ a/kernel/printk.c @@ -355,7 +355,7 @@ static ssize_t devkmsg_writev(struct kio int level = default_message_loglevel; int facility = 1; /* LOG_USER */ size_t len = iov_length(iv, count); - ssize_t ret = len; + ssize_t ret; if (len > LOG_LINE_MAX) return -EINVAL; @@ -365,8 +365,12 @@ static ssize_t devkmsg_writev(struct kio line = buf; for (i = 0; i < count; i++) { - if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) + if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) { + ret = line - buf; + if (!ret) + ret = -EFAULT; goto out; + } line += iv[i].iov_len; } @@ -396,6 +400,7 @@ static ssize_t devkmsg_writev(struct kio line[len] = '\0'; printk_emit(facility, level, NULL, 0, "%s", line); + ret = 0; out: kfree(buf); return ret; _
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