[PATCH] jfs: Use unsigned variable for length calculations

[PATCH] jfs: Use unsigned variable for length calculations

[Kees Cook]

To avoid confusing the compiler about possible negative sizes, switch
"ssize" which can never be negative from int to u32.  Seen with GCC 13:

../fs/jfs/namei.c: In function 'jfs_symlink': ../include/linux/fortify-string.h:57:33: warning: '__builtin_memcpy' pointer overflow between offset 0 and size [-2147483648, -1]
[-Warray-bounds=]
   57 | #define __underlying_memcpy     __builtin_memcpy
      |                                 ^
...
../fs/jfs/namei.c:950:17: note: in expansion of macro 'memcpy'
  950 |                 memcpy(ip->i_link, name, ssize);
      |                 ^~~~~~

Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: jfs-discussion@lists.sourceforge.net
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 fs/jfs/namei.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
index b29d68b5eec5..494b9f4043cf 100644
--- a/fs/jfs/namei.c
+++ b/fs/jfs/namei.c
@@ -876,7 +876,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
 	tid_t tid;
 	ino_t ino = 0;
 	struct component_name dname;
-	int ssize;		/* source pathname size */
+	u32 ssize;		/* source pathname size */
 	struct btstack btstack;
 	struct inode *ip = d_inode(dentry);
 	s64 xlen = 0;
@@ -957,7 +957,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
 		if (ssize > sizeof (JFS_IP(ip)->i_inline))
 			JFS_IP(ip)->mode2 &= ~INLINEEA;
 
-		jfs_info("jfs_symlink: fast symlink added  ssize:%d name:%s ",
+		jfs_info("jfs_symlink: fast symlink added  ssize:%u name:%s ",
 			 ssize, name);
 	}
 	/*
@@ -987,7 +987,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
 		ip->i_size = ssize - 1;
 		while (ssize) {
 			/* This is kind of silly since PATH_MAX == 4K */
-			int copy_size = min(ssize, PSIZE);
+			u32 copy_size = min_t(u32, ssize, PSIZE);
 
 			mp = get_metapage(ip, xaddr, PSIZE, 1);
 
-- 
2.34.1

Re: [PATCH] jfs: Use unsigned variable for length calculations

[Dr. David Alan Gilbert]

* Kees Cook (keescook@chromium.org) wrote:
> To avoid confusing the compiler about possible negative sizes, switch
> "ssize" which can never be negative from int to u32.  Seen with GCC 13:
> 
> ../fs/jfs/namei.c: In function 'jfs_symlink': ../include/linux/fortify-string.h:57:33: warning: '__builtin_memcpy' pointer overflow between offset 0 and size [-2147483648, -1]
> [-Warray-bounds=]
>    57 | #define __underlying_memcpy     __builtin_memcpy
>       |                                 ^
> ...
> ../fs/jfs/namei.c:950:17: note: in expansion of macro 'memcpy'
>   950 |                 memcpy(ip->i_link, name, ssize);
>       |                 ^~~~~~
> 
> Cc: Dave Kleikamp <shaggy@kernel.org>
> Cc: Christian Brauner <brauner@kernel.org>
> Cc: Dave Chinner <dchinner@redhat.com>
> Cc: jfs-discussion@lists.sourceforge.net
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  fs/jfs/namei.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
> index b29d68b5eec5..494b9f4043cf 100644
> --- a/fs/jfs/namei.c
> +++ b/fs/jfs/namei.c
> @@ -876,7 +876,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
>  	tid_t tid;
>  	ino_t ino = 0;
>  	struct component_name dname;
> -	int ssize;		/* source pathname size */
> +	u32 ssize;		/* source pathname size */

Had you considered using size_t - this is set from a strlen and used by a memcpy
that both talk size_t.

Dave

>  	struct btstack btstack;
>  	struct inode *ip = d_inode(dentry);
>  	s64 xlen = 0;
> @@ -957,7 +957,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
>  		if (ssize > sizeof (JFS_IP(ip)->i_inline))
>  			JFS_IP(ip)->mode2 &= ~INLINEEA;
>  
> -		jfs_info("jfs_symlink: fast symlink added  ssize:%d name:%s ",
> +		jfs_info("jfs_symlink: fast symlink added  ssize:%u name:%s ",
>  			 ssize, name);
>  	}
>  	/*
> @@ -987,7 +987,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
>  		ip->i_size = ssize - 1;
>  		while (ssize) {
>  			/* This is kind of silly since PATH_MAX == 4K */
> -			int copy_size = min(ssize, PSIZE);
> +			u32 copy_size = min_t(u32, ssize, PSIZE);
>  
>  			mp = get_metapage(ip, xaddr, PSIZE, 1);
>  
> -- 
> 2.34.1
> 
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/

Re: [PATCH] jfs: Use unsigned variable for length calculations

[Kees Cook]

On Sat, Feb 04, 2023 at 08:25:45PM +0000, Dr. David Alan Gilbert wrote:
> * Kees Cook (keescook@chromium.org) wrote:
> > To avoid confusing the compiler about possible negative sizes, switch
> > "ssize" which can never be negative from int to u32.  Seen with GCC 13:
> > 
> > ../fs/jfs/namei.c: In function 'jfs_symlink': ../include/linux/fortify-string.h:57:33: warning: '__builtin_memcpy' pointer overflow between offset 0 and size [-2147483648, -1]
> > [-Warray-bounds=]
> >    57 | #define __underlying_memcpy     __builtin_memcpy
> >       |                                 ^
> > ...
> > ../fs/jfs/namei.c:950:17: note: in expansion of macro 'memcpy'
> >   950 |                 memcpy(ip->i_link, name, ssize);
> >       |                 ^~~~~~
> > 
> > Cc: Dave Kleikamp <shaggy@kernel.org>
> > Cc: Christian Brauner <brauner@kernel.org>
> > Cc: Dave Chinner <dchinner@redhat.com>
> > Cc: jfs-discussion@lists.sourceforge.net
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> >  fs/jfs/namei.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
> > index b29d68b5eec5..494b9f4043cf 100644
> > --- a/fs/jfs/namei.c
> > +++ b/fs/jfs/namei.c
> > @@ -876,7 +876,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
> >  	tid_t tid;
> >  	ino_t ino = 0;
> >  	struct component_name dname;
> > -	int ssize;		/* source pathname size */
> > +	u32 ssize;		/* source pathname size */
> 
> Had you considered using size_t - this is set from a strlen and used by a memcpy
> that both talk size_t.

I considered that, but I've had other maintainers upset about doubling
the variable size. I opted to keep the variable 32-bit here, so the
machine code would only change to lose signed-ness.

-Kees

-- 
Kees Cook

Re: [PATCH] jfs: Use unsigned variable for length calculations

[Dr. David Alan Gilbert]

* Kees Cook (keescook@chromium.org) wrote:
> On Sat, Feb 04, 2023 at 08:25:45PM +0000, Dr. David Alan Gilbert wrote:
> > * Kees Cook (keescook@chromium.org) wrote:
> > > To avoid confusing the compiler about possible negative sizes, switch
> > > "ssize" which can never be negative from int to u32.  Seen with GCC 13:
> > > 
> > > ../fs/jfs/namei.c: In function 'jfs_symlink': ../include/linux/fortify-string.h:57:33: warning: '__builtin_memcpy' pointer overflow between offset 0 and size [-2147483648, -1]
> > > [-Warray-bounds=]
> > >    57 | #define __underlying_memcpy     __builtin_memcpy
> > >       |                                 ^
> > > ...
> > > ../fs/jfs/namei.c:950:17: note: in expansion of macro 'memcpy'
> > >   950 |                 memcpy(ip->i_link, name, ssize);
> > >       |                 ^~~~~~
> > > 
> > > Cc: Dave Kleikamp <shaggy@kernel.org>
> > > Cc: Christian Brauner <brauner@kernel.org>
> > > Cc: Dave Chinner <dchinner@redhat.com>
> > > Cc: jfs-discussion@lists.sourceforge.net
> > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > > ---
> > >  fs/jfs/namei.c | 6 +++---
> > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
> > > index b29d68b5eec5..494b9f4043cf 100644
> > > --- a/fs/jfs/namei.c
> > > +++ b/fs/jfs/namei.c
> > > @@ -876,7 +876,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
> > >  	tid_t tid;
> > >  	ino_t ino = 0;
> > >  	struct component_name dname;
> > > -	int ssize;		/* source pathname size */
> > > +	u32 ssize;		/* source pathname size */
> > 
> > Had you considered using size_t - this is set from a strlen and used by a memcpy
> > that both talk size_t.
> 
> I considered that, but I've had other maintainers upset about doubling
> the variable size.

I bet at least on some platforms it's cheaper as the 64 bit.

> I opted to keep the variable 32-bit here, so the
> machine code would only change to lose signed-ness.

Fair enough.

Dave

> -Kees
> 
> -- 
> Kees Cook
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/

Re: [PATCH] jfs: Use unsigned variable for length calculations

[Kees Cook]

On Mon, Feb 06, 2023 at 07:50:42PM +0000, Dr. David Alan Gilbert wrote:
> * Kees Cook (keescook@chromium.org) wrote:
> > On Sat, Feb 04, 2023 at 08:25:45PM +0000, Dr. David Alan Gilbert wrote:
> > > * Kees Cook (keescook@chromium.org) wrote:
> > > > To avoid confusing the compiler about possible negative sizes, switch
> > > > "ssize" which can never be negative from int to u32.  Seen with GCC 13:
> > > > 
> > > > ../fs/jfs/namei.c: In function 'jfs_symlink': ../include/linux/fortify-string.h:57:33: warning: '__builtin_memcpy' pointer overflow between offset 0 and size [-2147483648, -1]
> > > > [-Warray-bounds=]
> > > >    57 | #define __underlying_memcpy     __builtin_memcpy
> > > >       |                                 ^
> > > > ...
> > > > ../fs/jfs/namei.c:950:17: note: in expansion of macro 'memcpy'
> > > >   950 |                 memcpy(ip->i_link, name, ssize);
> > > >       |                 ^~~~~~
> > > > 
> > > > Cc: Dave Kleikamp <shaggy@kernel.org>
> > > > Cc: Christian Brauner <brauner@kernel.org>
> > > > Cc: Dave Chinner <dchinner@redhat.com>
> > > > Cc: jfs-discussion@lists.sourceforge.net
> > > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > > > ---
> > > >  fs/jfs/namei.c | 6 +++---
> > > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > > > 
> > > > diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
> > > > index b29d68b5eec5..494b9f4043cf 100644
> > > > --- a/fs/jfs/namei.c
> > > > +++ b/fs/jfs/namei.c
> > > > @@ -876,7 +876,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
> > > >  	tid_t tid;
> > > >  	ino_t ino = 0;
> > > >  	struct component_name dname;
> > > > -	int ssize;		/* source pathname size */
> > > > +	u32 ssize;		/* source pathname size */
> > > 
> > > Had you considered using size_t - this is set from a strlen and used by a memcpy
> > > that both talk size_t.
> > 
> > I considered that, but I've had other maintainers upset about doubling
> > the variable size.
> 
> I bet at least on some platforms it's cheaper as the 64 bit.
> 
> > I opted to keep the variable 32-bit here, so the
> > machine code would only change to lose signed-ness.
> 
> Fair enough.

Thread ping. Can someone pick this up (or Ack it for my tree), please?

Thanks!

-Kees

-- 
Kees Cook

Re: [PATCH] jfs: Use unsigned variable for length calculations

[Jeff Xu]

On Thu, Jun 1, 2023 at 9:55 AM Kees Cook <keescook@chromium.org> wrote:
>
> On Mon, Feb 06, 2023 at 07:50:42PM +0000, Dr. David Alan Gilbert wrote:
> > * Kees Cook (keescook@chromium.org) wrote:
> > > On Sat, Feb 04, 2023 at 08:25:45PM +0000, Dr. David Alan Gilbert wrote:
> > > > * Kees Cook (keescook@chromium.org) wrote:
> > > > > To avoid confusing the compiler about possible negative sizes, switch
> > > > > "ssize" which can never be negative from int to u32.  Seen with GCC 13:
> > > > >
> > > > > ../fs/jfs/namei.c: In function 'jfs_symlink': ../include/linux/fortify-string.h:57:33: warning: '__builtin_memcpy' pointer overflow between offset 0 and size [-2147483648, -1]
> > > > > [-Warray-bounds=]
> > > > >    57 | #define __underlying_memcpy     __builtin_memcpy
> > > > >       |                                 ^
> > > > > ...
> > > > > ../fs/jfs/namei.c:950:17: note: in expansion of macro 'memcpy'
> > > > >   950 |                 memcpy(ip->i_link, name, ssize);
> > > > >       |                 ^~~~~~
> > > > >
> > > > > Cc: Dave Kleikamp <shaggy@kernel.org>
> > > > > Cc: Christian Brauner <brauner@kernel.org>
> > > > > Cc: Dave Chinner <dchinner@redhat.com>
> > > > > Cc: jfs-discussion@lists.sourceforge.net
> > > > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > > > > ---
> > > > >  fs/jfs/namei.c | 6 +++---
> > > > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > > > >
> > > > > diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
> > > > > index b29d68b5eec5..494b9f4043cf 100644
> > > > > --- a/fs/jfs/namei.c
> > > > > +++ b/fs/jfs/namei.c
> > > > > @@ -876,7 +876,7 @@ static int jfs_symlink(struct mnt_idmap *idmap, struct inode *dip,
> > > > >         tid_t tid;
> > > > >         ino_t ino = 0;
> > > > >         struct component_name dname;
> > > > > -       int ssize;              /* source pathname size */
> > > > > +       u32 ssize;              /* source pathname size */
> > > >
> > > > Had you considered using size_t - this is set from a strlen and used by a memcpy
> > > > that both talk size_t.
> > >
> > > I considered that, but I've had other maintainers upset about doubling
> > > the variable size.
> >
> > I bet at least on some platforms it's cheaper as the 64 bit.
> >
> > > I opted to keep the variable 32-bit here, so the
> > > machine code would only change to lose signed-ness.
> >
> > Fair enough.
>
> Thread ping. Can someone pick this up (or Ack it for my tree), please?
>
Acked-by: Jeff Xu <jeffxu@chromium.org>

In case you ask someone to look at code, which I did.
Best
-Jeff


> Thanks!
>
> -Kees
>
> --
> Kees Cook

Re: [PATCH] jfs: Use unsigned variable for length calculations

[Christian Brauner]

On Sat, 04 Feb 2023 10:33:56 -0800, Kees Cook wrote:
> To avoid confusing the compiler about possible negative sizes, switch
> "ssize" which can never be negative from int to u32.  Seen with GCC 13:
> 
> ../fs/jfs/namei.c: In function 'jfs_symlink': ../include/linux/fortify-string.h:57:33: warning: '__builtin_memcpy' pointer overflow between offset 0 and size [-2147483648, -1]
> [-Warray-bounds=]
>    57 | #define __underlying_memcpy     __builtin_memcpy
>       |                                 ^
> ...
> ../fs/jfs/namei.c:950:17: note: in expansion of macro 'memcpy'
>   950 |                 memcpy(ip->i_link, name, ssize);
>       |                 ^~~~~~
> 
> [...]

Applied to the vfs.misc branch of the vfs/vfs.git tree.
Patches in the vfs.misc branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.misc

[1/1] jfs: Use unsigned variable for length calculations
      https://git.kernel.org/vfs/vfs/c/2d6e1895d440

Re: [PATCH] jfs: Use unsigned variable for length calculations

[Dave Kleikamp]

I apologize to all of you for letting this one go so long.

Acked-by: Dave Kleikamp <dave.kleikamp@oracle.com>

On 6/2/23 3:32AM, Christian Brauner wrote:
> On Sat, 04 Feb 2023 10:33:56 -0800, Kees Cook wrote:
>> To avoid confusing the compiler about possible negative sizes, switch
>> "ssize" which can never be negative from int to u32.  Seen with GCC 13:
>>
>> ../fs/jfs/namei.c: In function 'jfs_symlink': ../include/linux/fortify-string.h:57:33: warning: '__builtin_memcpy' pointer overflow between offset 0 and size [-2147483648, -1]
>> [-Warray-bounds=]
>>     57 | #define __underlying_memcpy     __builtin_memcpy
>>        |                                 ^
>> ...
>> ../fs/jfs/namei.c:950:17: note: in expansion of macro 'memcpy'
>>    950 |                 memcpy(ip->i_link, name, ssize);
>>        |                 ^~~~~~
>>
>> [...]
> 
> Applied to the vfs.misc branch of the vfs/vfs.git tree.
> Patches in the vfs.misc branch should appear in linux-next soon.
> 
> Please report any outstanding bugs that were missed during review in a
> new review to the original patch series allowing us to drop it.
> 
> It's encouraged to provide Acked-bys and Reviewed-bys even though the
> patch has now been applied. If possible patch trailers will be updated.
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
> branch: vfs.misc
> 
> [1/1] jfs: Use unsigned variable for length calculations
>        https://git.kernel.org/vfs/vfs/c/2d6e1895d440

RE: [PATCH] jfs: Use unsigned variable for length calculations

[David Laight]

From: Kees Cook
> Sent: 01 June 2023 17:55
> 
> On Mon, Feb 06, 2023 at 07:50:42PM +0000, Dr. David Alan Gilbert wrote:
> > * Kees Cook (keescook@chromium.org) wrote:
> > > On Sat, Feb 04, 2023 at 08:25:45PM +0000, Dr. David Alan Gilbert wrote:
...
> > > > > -	int ssize;		/* source pathname size */
> > > > > +	u32 ssize;		/* source pathname size */
> > > >
> > > > Had you considered using size_t - this is set from a strlen and used by a memcpy
> > > > that both talk size_t.
> > >
> > > I considered that, but I've had other maintainers upset about doubling
> > > the variable size.
> >
> > I bet at least on some platforms it's cheaper as the 64 bit.
> >
> > > I opted to keep the variable 32-bit here, so the
> > > machine code would only change to lose signed-ness.

On x86-64 'unsigned int' and 'signed long' are likely to
generate the best code.

If you use 'signed int' it will to have to be sign extended
if used in a 64-bit expression (eg as an array index).

(That is probably true of most 64bit arch.)

OTOH 'unsigned long' always requires a REX prefix - making the
code that bit larger.

	David

-
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