Fix SCSI generic read() incorrectly returning success after detecting an
error.
Cc: <[email protected]>
Signed-off-by: Tony Battersby <[email protected]>
---
For inclusion in kernel 3.20.
--- linux-3.19.0/drivers/scsi/sg.c.orig 2015-02-08 21:54:22.000000000 -0500
+++ linux-3.19.0/drivers/scsi/sg.c 2015-02-10 09:26:09.000000000 -0500
@@ -546,7 +546,7 @@ static ssize_t
sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp)
{
sg_io_hdr_t *hp = &srp->header;
- int err = 0;
+ int err = 0, err2;
int len;
if (count < SZ_SG_IO_HDR) {
@@ -575,8 +575,8 @@ sg_new_read(Sg_fd * sfp, char __user *bu
goto err_out;
}
err_out:
- err = sg_finish_rem_req(srp);
- return (0 == err) ? count : err;
+ err2 = sg_finish_rem_req(srp);
+ return err ? : err2 ? : count;
}
static ssize_t
On 15-02-11 11:32 AM, Tony Battersby wrote:
> Fix SCSI generic read() incorrectly returning success after detecting an
> error.
>
> Cc: <[email protected]>
> Signed-off-by: Tony Battersby <[email protected]>
> ---
>
> For inclusion in kernel 3.20.
>
> --- linux-3.19.0/drivers/scsi/sg.c.orig 2015-02-08 21:54:22.000000000 -0500
> +++ linux-3.19.0/drivers/scsi/sg.c 2015-02-10 09:26:09.000000000 -0500
> @@ -546,7 +546,7 @@ static ssize_t
> sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp)
> {
> sg_io_hdr_t *hp = &srp->header;
> - int err = 0;
> + int err = 0, err2;
> int len;
>
> if (count < SZ_SG_IO_HDR) {
> @@ -575,8 +575,8 @@ sg_new_read(Sg_fd * sfp, char __user *bu
> goto err_out;
> }
> err_out:
> - err = sg_finish_rem_req(srp);
> - return (0 == err) ? count : err;
> + err2 = sg_finish_rem_req(srp);
> + return err ? : err2 ? : count;
Tony,
Your point is well made.
I just don't like that last line, using a gcc extension that
hasn't even made it into C11 (or C++11). Wouldn't:
return err ? err : (err2 ? err2 : count);
be a bit better? I think the following snippet makes the intent
clear but would it generate any more code:
if (err || err2)
return err ? err : err2;
else
return count;
Doug Gilbert
On 02/11/2015 12:45 PM, Douglas Gilbert wrote:
> On 15-02-11 11:32 AM, Tony Battersby wrote:
>> Fix SCSI generic read() incorrectly returning success after detecting an
>> error.
>>
>> Cc: <[email protected]>
>> Signed-off-by: Tony Battersby <[email protected]>
>> ---
>>
>> For inclusion in kernel 3.20.
>>
>> --- linux-3.19.0/drivers/scsi/sg.c.orig 2015-02-08 21:54:22.000000000 -0500
>> +++ linux-3.19.0/drivers/scsi/sg.c 2015-02-10 09:26:09.000000000 -0500
>> @@ -546,7 +546,7 @@ static ssize_t
>> sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp)
>> {
>> sg_io_hdr_t *hp = &srp->header;
>> - int err = 0;
>> + int err = 0, err2;
>> int len;
>>
>> if (count < SZ_SG_IO_HDR) {
>> @@ -575,8 +575,8 @@ sg_new_read(Sg_fd * sfp, char __user *bu
>> goto err_out;
>> }
>> err_out:
>> - err = sg_finish_rem_req(srp);
>> - return (0 == err) ? count : err;
>> + err2 = sg_finish_rem_req(srp);
>> + return err ? : err2 ? : count;
> Tony,
> Your point is well made.
>
> I just don't like that last line, using a gcc extension that
> hasn't even made it into C11 (or C++11). Wouldn't:
> return err ? err : (err2 ? err2 : count);
>
> be a bit better? I think the following snippet makes the intent
> clear but would it generate any more code:
> if (err || err2)
> return err ? err : err2;
> else
> return count;
>
> Doug Gilbert
>
>
>
I checked before submitting, and the foo ? : bar construct is already
used at least 455 times in the kernel, so it is nothing new.
find linux-3.19 -type f -name "*.[ch]" | xargs grep '\? :' | wc -l
455
But you are probably right; I think that with such small variable names
your version is more readable due to the nesting. Updated patch below.
---
Fix SCSI generic read() incorrectly returning success after detecting an
error.
Cc: <[email protected]>
Signed-off-by: Tony Battersby <[email protected]>
---
--- linux-3.19.0/drivers/scsi/sg.c.orig 2015-02-08 21:54:22.000000000 -0500
+++ linux-3.19.0/drivers/scsi/sg.c 2015-02-11 13:02:56.000000000 -0500
@@ -546,7 +546,7 @@ static ssize_t
sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp)
{
sg_io_hdr_t *hp = &srp->header;
- int err = 0;
+ int err = 0, err2;
int len;
if (count < SZ_SG_IO_HDR) {
@@ -575,8 +575,8 @@ sg_new_read(Sg_fd * sfp, char __user *bu
goto err_out;
}
err_out:
- err = sg_finish_rem_req(srp);
- return (0 == err) ? count : err;
+ err2 = sg_finish_rem_req(srp);
+ return err ? err : (err2 ? err2 : count);
}
static ssize_t
On 15-02-11 01:13 PM, Tony Battersby wrote:
> On 02/11/2015 12:45 PM, Douglas Gilbert wrote:
>> On 15-02-11 11:32 AM, Tony Battersby wrote:
>>> Fix SCSI generic read() incorrectly returning success after detecting an
>>> error.
>>>
>>> Cc: <[email protected]>
>>> Signed-off-by: Tony Battersby <[email protected]>
>>> ---
>>>
>>> For inclusion in kernel 3.20.
>>>
>>> --- linux-3.19.0/drivers/scsi/sg.c.orig 2015-02-08 21:54:22.000000000 -0500
>>> +++ linux-3.19.0/drivers/scsi/sg.c 2015-02-10 09:26:09.000000000 -0500
>>> @@ -546,7 +546,7 @@ static ssize_t
>>> sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp)
>>> {
>>> sg_io_hdr_t *hp = &srp->header;
>>> - int err = 0;
>>> + int err = 0, err2;
>>> int len;
>>>
>>> if (count < SZ_SG_IO_HDR) {
>>> @@ -575,8 +575,8 @@ sg_new_read(Sg_fd * sfp, char __user *bu
>>> goto err_out;
>>> }
>>> err_out:
>>> - err = sg_finish_rem_req(srp);
>>> - return (0 == err) ? count : err;
>>> + err2 = sg_finish_rem_req(srp);
>>> + return err ? : err2 ? : count;
>> Tony,
>> Your point is well made.
>>
>> I just don't like that last line, using a gcc extension that
>> hasn't even made it into C11 (or C++11). Wouldn't:
>> return err ? err : (err2 ? err2 : count);
>>
>> be a bit better? I think the following snippet makes the intent
>> clear but would it generate any more code:
>> if (err || err2)
An improvement on the above line would be:
if (unlikely(err || err2))
>> return err ? err : err2;
>> else
>> return count;
>>
Another approach is to return the good path prior to the
err_out label. This would require two calls to
sg_finish_rem_req().
However Tony's clean-up is sufficient.
> I checked before submitting, and the foo ? : bar construct is already
> used at least 455 times in the kernel, so it is nothing new.
>
> find linux-3.19 -type f -name "*.[ch]" | xargs grep '\? :' | wc -l
> 455
>
> But you are probably right; I think that with such small variable names
> your version is more readable due to the nesting. Updated patch below.
>
> ---
>
> Fix SCSI generic read() incorrectly returning success after detecting an
> error.
>
> Cc: <[email protected]>
> Signed-off-by: Tony Battersby <[email protected]>
Acked-by: Douglas Gilbert <[email protected]>
> ---
>
> --- linux-3.19.0/drivers/scsi/sg.c.orig 2015-02-08 21:54:22.000000000 -0500
> +++ linux-3.19.0/drivers/scsi/sg.c 2015-02-11 13:02:56.000000000 -0500
> @@ -546,7 +546,7 @@ static ssize_t
> sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp)
> {
> sg_io_hdr_t *hp = &srp->header;
> - int err = 0;
> + int err = 0, err2;
> int len;
>
> if (count < SZ_SG_IO_HDR) {
> @@ -575,8 +575,8 @@ sg_new_read(Sg_fd * sfp, char __user *bu
> goto err_out;
> }
> err_out:
> - err = sg_finish_rem_req(srp);
> - return (0 == err) ? count : err;
> + err2 = sg_finish_rem_req(srp);
> + return err ? err : (err2 ? err2 : count);
> }
>
> static ssize_t
>
> --