3.16-rc6 -- fs/direct-io.c:1011 from and to uninitialized.

RFC In review Ian Kumlien 3 participants 5 messages Jul 22, 2014 VFS

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Ian Kumlien

author

2014-07-22 19:04 UTC #0 lore raw

RFC 1/1 3.16-rc6 -- fs/direct-io.c:1011 from and to uninitialized.

This is a resend, try two...

---
Hi,

While playing around compiling the kernel i noticed the following:
fs/direct-io.c: In function ‘do_blockdev_direct_IO’:
fs/direct-io.c:1022:29: warning: ‘from’ may be used uninitialized in this function [-Wmaybe-uninitialized]
ret = submit_page_section(dio, sdio, page,
^
fs/direct-io.c:913:10: note: ‘from’ was declared here

   size_t from, to;
          ^
fs/direct-io.c:1011:12: warning: ‘to’ may be used uninitialized in this
function [-Wmaybe-uninitialized]
    u = (to - from) >> blkbits;
            ^
fs/direct-io.c:913:16: note: ‘to’ was declared here
   size_t from, to;
                ^

---

And while the fix is simple, something along the lines of:

fs/direct-io.c +0 -0

index 98040ba..64a8286 100644
@@ -910,7 +910,7 @@ static int do_direct_IO(struct dio *dio, struct

dio_submit *sdi

        while (sdio->block_in_file < sdio->final_block_in_request) {
                struct page *page;
-               size_t from, to;
+               size_t from, to = {0};
                page = dio_get_page(dio, sdio, &from, &to);
                if (IS_ERR(page)) {
                        ret = PTR_ERR(page);

---

I however don't know if it's in the correct C standard, it compiles fine though... (or if this is more gcc speific)

commit f94d05ce10d869c418d3271bd028fc33bfd25e6f

Author: Ian Kumlien <[email protected]>
Date:   Tue Jul 22 20:57:50 2014 +0200

Initialize the to and from fields

While compliling the 3.16-rc6 kernel I saw this:
fs/direct-io.c: In function ‘do_blockdev_direct_IO’:
fs/direct-io.c:1022:29: warning: ‘from’ may be used uninitialized in this function [-Wmaybe-uninitialized]
ret = submit_page_section(dio, sdio, page,
^
fs/direct-io.c:913:10: note: ‘from’ was declared here
size_t from, to;
^
fs/direct-io.c:1011:12: warning: ‘to’ may be used uninitialized in this function [-Wmaybe-uninitialized]
u = (to - from) >> blkbits;
^
fs/direct-io.c:913:16: note: ‘to’ was declared here
size_t from, to;
^
---

This small changes makes sure that the values are initialized.

Signed-off-by Ian Kumlien <[email protected]>

fs/direct-io.c +1 -1

index 98040ba..64a8286 100644
@@ -910,7 +910,7 @@ static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
 
        while (sdio->block_in_file < sdio->final_block_in_request) {
                struct page *page;
-               size_t from, to;
+               size_t from, to = {0};
                page = dio_get_page(dio, sdio, &from, &to);
                if (IS_ERR(page)) {
                        ret = PTR_ERR(page);

Richard Weinberger

2014-07-22 19:12 UTC #1 lore raw

Quoted 1 line · Ian Kumlien

This is a resend, try two...

Please see "[PATCH v3] direct-io: fix uninitialized warning in do_direct_IO()".

Quoted 44 lines

---
Hi,
While playing around compiling the kernel i noticed the following:
fs/direct-io.c: In function ‘do_blockdev_direct_IO’:
fs/direct-io.c:1022:29: warning: ‘from’ may be used uninitialized in this function [-Wmaybe-uninitialized]
ret = submit_page_section(dio, sdio, page,
^
fs/direct-io.c:913:10: note: ‘from’ was declared here
   size_t from, to;
          ^
fs/direct-io.c:1011:12: warning: ‘to’ may be used uninitialized in this
function [-Wmaybe-uninitialized]
    u = (to - from) >> blkbits;
            ^
fs/direct-io.c:913:16: note: ‘to’ was declared here
   size_t from, to;
                ^
---
And while the fix is simple, something along the lines of:
fs/direct-io.c +0 -0
index 98040ba..64a8286 100644
@@ -910,7 +910,7 @@ static int do_direct_IO(struct dio *dio, struct
dio_submit *sdi
        while (sdio->block_in_file < sdio->final_block_in_request) {
                struct page *page;
fs/direct-io.c +1 -2
-               size_t from, to;
+               size_t from, to = {0};
                page = dio_get_page(dio, sdio, &from, &to);
                if (IS_ERR(page)) {
                        ret = PTR_ERR(page);
---
I however don't know if it's in the correct C standard, it compiles fine though... (or if this is more gcc speific)

Signature · 2 lines

Thanks,
//richard

Ian Kumlien

author

2014-07-22 19:18 UTC #2 lore raw

Quoted 4 lines · Richard Weinberger

Quoted 1 line · Ian Kumlien
This is a resend, try two...
Please see "[PATCH v3] direct-io: fix uninitialized warning in do_direct_IO()".

That looks like a better approach, couldn't find it before i started sending this and my emails are autofiltered if you send via the web ui.. ;)

Quoted 47 lines

Quoted 44 lines
---
Hi,
While playing around compiling the kernel i noticed the following:
fs/direct-io.c: In function ‘do_blockdev_direct_IO’:
fs/direct-io.c:1022:29: warning: ‘from’ may be used uninitialized in this function [-Wmaybe-uninitialized]
ret = submit_page_section(dio, sdio, page,
^
fs/direct-io.c:913:10: note: ‘from’ was declared here
   size_t from, to;
          ^
fs/direct-io.c:1011:12: warning: ‘to’ may be used uninitialized in this
function [-Wmaybe-uninitialized]
    u = (to - from) >> blkbits;
            ^
fs/direct-io.c:913:16: note: ‘to’ was declared here
   size_t from, to;
                ^
---
And while the fix is simple, something along the lines of:
fs/direct-io.c +0 -0
index 98040ba..64a8286 100644
@@ -910,7 +910,7 @@ static int do_direct_IO(struct dio *dio, struct
dio_submit *sdi
        while (sdio->block_in_file < sdio->final_block_in_request) {
                struct page *page;
fs/direct-io.c +1 -2
-               size_t from, to;
+               size_t from, to = {0};
                page = dio_get_page(dio, sdio, &from, &to);
                if (IS_ERR(page)) {
                        ret = PTR_ERR(page);
---
I however don't know if it's in the correct C standard, it compiles fine though... (or if this is more gcc speific)

Randy Dunlap

2014-07-22 19:20 UTC #3 lore raw

In reply to Ian Kumlien

Quoted 41 lines · Ian Kumlien

This is a resend, try two...
---
Hi,
While playing around compiling the kernel i noticed the following:
fs/direct-io.c: In function ‘do_blockdev_direct_IO’:
fs/direct-io.c:1022:29: warning: ‘from’ may be used uninitialized in this function [-Wmaybe-uninitialized]
ret = submit_page_section(dio, sdio, page,
^
fs/direct-io.c:913:10: note: ‘from’ was declared here
   size_t from, to;
          ^
fs/direct-io.c:1011:12: warning: ‘to’ may be used uninitialized in this
function [-Wmaybe-uninitialized]
    u = (to - from) >> blkbits;
            ^
fs/direct-io.c:913:16: note: ‘to’ was declared here
   size_t from, to;
                ^
---
And while the fix is simple, something along the lines of:
fs/direct-io.c +0 -0
index 98040ba..64a8286 100644
@@ -910,7 +910,7 @@ static int do_direct_IO(struct dio *dio, struct
dio_submit *sdi
        while (sdio->block_in_file < sdio->final_block_in_request) {
                struct page *page;
fs/direct-io.c +1 -2
-               size_t from, to;
+               size_t from, to = {0};
                page = dio_get_page(dio, sdio, &from, &to);
                if (IS_ERR(page)) {
                        ret = PTR_ERR(page);
---

Quoted 2 lines

I however don't know if it's in the correct C standard, it compiles fine though... (or if this is more gcc speific)

so... do you know C or not?

Why the braces around the 0?

Why do you initialize 'to' but not 'from'?

Signature · 1 line

~Randy

Ian Kumlien

author

2014-07-22 19:24 UTC #4 lore raw

Quoted 20 lines · Randy Dunlap

Quoted 19 lines · Ian Kumlien

This is a resend, try two...

And while the fix is simple, something along the lines of:

fs/direct-io.c +0 -0

index 98040ba..64a8286 100644
@@ -910,7 +910,7 @@ static int do_direct_IO(struct dio *dio, struct

dio_submit *sdi

        while (sdio->block_in_file < sdio->final_block_in_request) {
                struct page *page;

fs/direct-io.c +1 -2

-               size_t from, to;
+               size_t from, to = {0};
                page = dio_get_page(dio, sdio, &from, &to);
                if (IS_ERR(page)) {
                        ret = PTR_ERR(page);
---

Quoted 4 lines

Quoted 2 lines
I however don't know if it's in the correct C standard, it compiles fine though... (or if this is more gcc speific)
so... do you know C or not?

I know C but i don't know if this got added in C99 or C11 or how they denote it.

Quoted 1 line

Why the braces around the 0?

Because it's special

Quoted 1 line

Why do you initialize 'to' but not 'from'?

The magic of {0} is that it will initialize all your values.