Re: [PATCH 5/6] lirc_zilog: error out if buffer read bytes != chunk size
On Wed, Mar 16, 2011 at 08:07:22PM -0400, Andy Walls wrote:
On Wed, 2011-03-16 at 16:24 -0400, Jarod Wilson wrote:
Signed-off-by: Jarod Wilson ja...@redhat.com
---
drivers/staging/lirc/lirc_zilog.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/drivers/staging/lirc/lirc_zilog.c
b/drivers/staging/lirc/lirc_zilog.c
index 407d4b4..5ada643 100644
--- a/drivers/staging/lirc/lirc_zilog.c
+++ b/drivers/staging/lirc/lirc_zilog.c
@@ -950,6 +950,10 @@ static ssize_t read(struct file *filep, char *outbuf,
size_t n, loff_t *ppos)
ret = copy_to_user((void *)outbuf+written, buf,
rbuf-chunk_size);
written += rbuf-chunk_size;
+ } else {
+ zilog_error(Buffer read failed!\n);
+ ret = -EIO;
+ break;
No need to break, just let the non-0 ret value drop you out of the while
loop.
Ah, indeed. I think I mindlessly copied what the tests just a few lines
above were doing without looking at the actual reason for them. I'll
remove that break from the patch here locally.
--
Jarod Wilson
ja...@redhat.com
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Re: [PATCH 5/6] lirc_zilog: error out if buffer read bytes != chunk size
Jarod Wilson ja...@redhat.com wrote:
On Wed, Mar 16, 2011 at 08:07:22PM -0400, Andy Walls wrote:
On Wed, 2011-03-16 at 16:24 -0400, Jarod Wilson wrote:
Signed-off-by: Jarod Wilson ja...@redhat.com
---
drivers/staging/lirc/lirc_zilog.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/drivers/staging/lirc/lirc_zilog.c
b/drivers/staging/lirc/lirc_zilog.c
index 407d4b4..5ada643 100644
--- a/drivers/staging/lirc/lirc_zilog.c
+++ b/drivers/staging/lirc/lirc_zilog.c
@@ -950,6 +950,10 @@ static ssize_t read(struct file *filep, char
*outbuf, size_t n, loff_t *ppos)
ret = copy_to_user((void *)outbuf+written, buf,
rbuf-chunk_size);
written += rbuf-chunk_size;
+ } else {
+ zilog_error(Buffer read failed!\n);
+ ret = -EIO;
+ break;
No need to break, just let the non-0 ret value drop you out of the
while
loop.
Ah, indeed. I think I mindlessly copied what the tests just a few lines
above were doing without looking at the actual reason for them. I'll
remove that break from the patch here locally.
--
Jarod Wilson
ja...@redhat.com
You might also want to take a look at that test to ensure it doesn't break
blocking read() behavior. (man 2 read). I'm swamped ATM and didn't look too
hard.
It seems odd that the lirc buffer object can have data ready (the first branch
of the big if() in the while() loop), and yet the read of that lirc buffer
object fails.
-Andy
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Re: [PATCH 5/6] lirc_zilog: error out if buffer read bytes != chunk size
On Thu, Mar 17, 2011 at 11:29:08AM -0400, Andy Walls wrote:
Jarod Wilson ja...@redhat.com wrote:
On Wed, Mar 16, 2011 at 08:07:22PM -0400, Andy Walls wrote:
On Wed, 2011-03-16 at 16:24 -0400, Jarod Wilson wrote:
Signed-off-by: Jarod Wilson ja...@redhat.com
---
drivers/staging/lirc/lirc_zilog.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/drivers/staging/lirc/lirc_zilog.c
b/drivers/staging/lirc/lirc_zilog.c
index 407d4b4..5ada643 100644
--- a/drivers/staging/lirc/lirc_zilog.c
+++ b/drivers/staging/lirc/lirc_zilog.c
@@ -950,6 +950,10 @@ static ssize_t read(struct file *filep, char
*outbuf, size_t n, loff_t *ppos)
ret = copy_to_user((void
*)outbuf+written, buf,
rbuf-chunk_size);
written += rbuf-chunk_size;
+} else {
+zilog_error(Buffer read failed!\n);
+ret = -EIO;
+break;
No need to break, just let the non-0 ret value drop you out of the
while
loop.
Ah, indeed. I think I mindlessly copied what the tests just a few lines
above were doing without looking at the actual reason for them. I'll
remove that break from the patch here locally.
--
Jarod Wilson
ja...@redhat.com
You might also want to take a look at that test to ensure it doesn't break
blocking read() behavior. (man 2 read). I'm swamped ATM and didn't look too
hard.
It seems odd that the lirc buffer object can have data ready (the first
branch of the big if() in the while() loop), and yet the read of that lirc
buffer object fails.
Generally, it shouldn't, but lirc_buffer_read uses kfifo underneath, and
in the pre-2.6.33 kfifo implementation, the retval from lirc_buffer_read
(as backported by way of media_build) is always 0, which is of course not
equal to chunk_size. So I think that in current kernels, this should never
trigger, and its partially just a note-to-self that this check will go
sideways when running on an older kernel, but not a bad check to have if
something really does go wrong.
--
Jarod Wilson
ja...@redhat.com
--
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Re: [PATCH 5/6] lirc_zilog: error out if buffer read bytes != chunk size
Jarod Wilson ja...@redhat.com wrote:
On Thu, Mar 17, 2011 at 11:29:08AM -0400, Andy Walls wrote:
Jarod Wilson ja...@redhat.com wrote:
On Wed, Mar 16, 2011 at 08:07:22PM -0400, Andy Walls wrote:
On Wed, 2011-03-16 at 16:24 -0400, Jarod Wilson wrote:
Signed-off-by: Jarod Wilson ja...@redhat.com
---
drivers/staging/lirc/lirc_zilog.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/drivers/staging/lirc/lirc_zilog.c
b/drivers/staging/lirc/lirc_zilog.c
index 407d4b4..5ada643 100644
--- a/drivers/staging/lirc/lirc_zilog.c
+++ b/drivers/staging/lirc/lirc_zilog.c
@@ -950,6 +950,10 @@ static ssize_t read(struct file *filep,
char
*outbuf, size_t n, loff_t *ppos)
ret = copy_to_user((void
*)outbuf+written, buf,
rbuf-chunk_size);
written += rbuf-chunk_size;
+ } else {
+ zilog_error(Buffer read failed!\n);
+ ret = -EIO;
+ break;
No need to break, just let the non-0 ret value drop you out of the
while
loop.
Ah, indeed. I think I mindlessly copied what the tests just a few
lines
above were doing without looking at the actual reason for them. I'll
remove that break from the patch here locally.
--
Jarod Wilson
ja...@redhat.com
You might also want to take a look at that test to ensure it doesn't
break blocking read() behavior. (man 2 read). I'm swamped ATM and
didn't look too hard.
It seems odd that the lirc buffer object can have data ready (the
first branch of the big if() in the while() loop), and yet the read of
that lirc buffer object fails.
Generally, it shouldn't, but lirc_buffer_read uses kfifo underneath,
and
in the pre-2.6.33 kfifo implementation, the retval from
lirc_buffer_read
(as backported by way of media_build) is always 0, which is of course
not
equal to chunk_size. So I think that in current kernels, this should
never
trigger, and its partially just a note-to-self that this check will go
sideways when running on an older kernel, but not a bad check to have
if
something really does go wrong.
--
Jarod Wilson
ja...@redhat.com
But the orignal intent of the check I put in was to avoid passing partial/junk
data to userspace, and go around again to see if good data could be provided.
Your check bails when good data that might be sitting there still. That
doesn't seem like a good trade for supporting backward compat for old kernels.
-Andy
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Re: [PATCH 5/6] lirc_zilog: error out if buffer read bytes != chunk size
On Thu, Mar 17, 2011 at 12:16:31PM -0400, Andy Walls wrote:
Jarod Wilson ja...@redhat.com wrote:
On Thu, Mar 17, 2011 at 11:29:08AM -0400, Andy Walls wrote:
Jarod Wilson ja...@redhat.com wrote:
On Wed, Mar 16, 2011 at 08:07:22PM -0400, Andy Walls wrote:
On Wed, 2011-03-16 at 16:24 -0400, Jarod Wilson wrote:
Signed-off-by: Jarod Wilson ja...@redhat.com
---
drivers/staging/lirc/lirc_zilog.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/drivers/staging/lirc/lirc_zilog.c
b/drivers/staging/lirc/lirc_zilog.c
index 407d4b4..5ada643 100644
--- a/drivers/staging/lirc/lirc_zilog.c
+++ b/drivers/staging/lirc/lirc_zilog.c
@@ -950,6 +950,10 @@ static ssize_t read(struct file *filep,
char
*outbuf, size_t n, loff_t *ppos)
ret = copy_to_user((void
*)outbuf+written, buf,
rbuf-chunk_size);
written += rbuf-chunk_size;
+ } else {
+ zilog_error(Buffer read failed!\n);
+ ret = -EIO;
+ break;
No need to break, just let the non-0 ret value drop you out of the
while
loop.
Ah, indeed. I think I mindlessly copied what the tests just a few
lines
above were doing without looking at the actual reason for them. I'll
remove that break from the patch here locally.
--
Jarod Wilson
ja...@redhat.com
You might also want to take a look at that test to ensure it doesn't
break blocking read() behavior. (man 2 read). I'm swamped ATM and
didn't look too hard.
It seems odd that the lirc buffer object can have data ready (the
first branch of the big if() in the while() loop), and yet the read of
that lirc buffer object fails.
Generally, it shouldn't, but lirc_buffer_read uses kfifo underneath,
and
in the pre-2.6.33 kfifo implementation, the retval from
lirc_buffer_read
(as backported by way of media_build) is always 0, which is of course
not
equal to chunk_size. So I think that in current kernels, this should
never
trigger, and its partially just a note-to-self that this check will go
sideways when running on an older kernel, but not a bad check to have
if
something really does go wrong.
But the orignal intent of the check I put in was to avoid passing
partial/junk data to userspace, and go around again to see if good data could
be provided.
Your check bails when good data that might be sitting there still. That
doesn't seem like a good trade for supporting backward compat for old kernels.
Ah. Another thing I neglected to notice then. :)
Perhaps there should be a retry count check as well then, as otherwise,
its possible to get stuck in that loop forever (which is what was
happening on older kernels). Its conceivable that similar could happen on
a newer kernel for some reason.
--
Jarod Wilson
ja...@redhat.com
--
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Re: [PATCH 5/6] lirc_zilog: error out if buffer read bytes != chunk size
On Thu, 2011-03-17 at 15:08 -0400, Jarod Wilson wrote: On Thu, Mar 17, 2011 at 12:16:31PM -0400, Andy Walls wrote: Jarod Wilson ja...@redhat.com wrote: . But the orignal intent of the check I put in was to avoid passing partial/junk data to userspace, and go around again to see if good data could be provided. Your check bails when good data that might be sitting there still. That doesn't seem like a good trade for supporting backward compat for old kernels. Ah. Another thing I neglected to notice then. :) Perhaps there should be a retry count check as well then, as otherwise, its possible to get stuck in that loop forever (which is what was happening on older kernels). Its conceivable that similar could happen on a newer kernel for some reason. Well, lets see, From the perspective of userspace lircd: 1. A specification compliance failure for a corner case isn't too bad (bailing out on junk and leaving good data behind) 2. An unrecoverable failure for any case is very bad (spinning/hanging on a result that won't change) 3. Sending unitialized bytes out to userspace with copy_to_user() is very bad. (I recall the old code would do the copy to user and always tell userspace it got a code whether it read anything out of the buffer or not. IIRC, that leaked information off the stack.) If the code as patched avoids the two very bad things (#2 and #3), then the patch is OK by me. Regards, Andy -- To unsubscribe from this list: send the line unsubscribe linux-media in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH 5/6] lirc_zilog: error out if buffer read bytes != chunk size
Signed-off-by: Jarod Wilson ja...@redhat.com
---
drivers/staging/lirc/lirc_zilog.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/drivers/staging/lirc/lirc_zilog.c
b/drivers/staging/lirc/lirc_zilog.c
index 407d4b4..5ada643 100644
--- a/drivers/staging/lirc/lirc_zilog.c
+++ b/drivers/staging/lirc/lirc_zilog.c
@@ -950,6 +950,10 @@ static ssize_t read(struct file *filep, char *outbuf,
size_t n, loff_t *ppos)
ret = copy_to_user((void *)outbuf+written, buf,
rbuf-chunk_size);
written += rbuf-chunk_size;
+ } else {
+ zilog_error(Buffer read failed!\n);
+ ret = -EIO;
+ break;
}
}
}
--
1.7.1
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Re: [PATCH 5/6] lirc_zilog: error out if buffer read bytes != chunk size
On Wed, 2011-03-16 at 16:24 -0400, Jarod Wilson wrote:
Signed-off-by: Jarod Wilson ja...@redhat.com
---
drivers/staging/lirc/lirc_zilog.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/drivers/staging/lirc/lirc_zilog.c
b/drivers/staging/lirc/lirc_zilog.c
index 407d4b4..5ada643 100644
--- a/drivers/staging/lirc/lirc_zilog.c
+++ b/drivers/staging/lirc/lirc_zilog.c
@@ -950,6 +950,10 @@ static ssize_t read(struct file *filep, char *outbuf,
size_t n, loff_t *ppos)
ret = copy_to_user((void *)outbuf+written, buf,
rbuf-chunk_size);
written += rbuf-chunk_size;
+ } else {
+ zilog_error(Buffer read failed!\n);
+ ret = -EIO;
+ break;
No need to break, just let the non-0 ret value drop you out of the while
loop.
Regards,
Andy
}
}
}
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