[PATCH v1 2/3] xfs/libxfs: replace kmalloc() and memcpy() with kmemdup()

[Andrey Albershteyn]

On 2024-12-18 16:35:21, Darrick J. Wong wrote:
> On Tue, Dec 17, 2024 at 11:58:12PM +0100, Mirsad Todorovac wrote:
> > The source static analysis tool gave the following advice:
> > 
> > ./fs/xfs/libxfs/xfs_dir2.c:382:15-22: WARNING opportunity for kmemdup
> > 
> >  → 382         args->value = kmalloc(len,
> >    383                          GFP_KERNEL | __GFP_NOLOCKDEP | __GFP_RETRY_MAYFAIL);
> >    384         if (!args->value)
> >    385                 return -ENOMEM;
> >    386
> >  → 387         memcpy(args->value, name, len);
> >    388         args->valuelen = len;
> >    389         return -EEXIST;
> > 
> > Replacing kmalloc() + memcpy() with kmemdump() doesn't change semantics.
> > Original code works without fault, so this is not a bug fix but proposed improvement.
> 
> I guess this is all right, but seeing as this code is shared with
> userspace ("libxfs"), making this change will just add to the wrappers
> that we have to have:
> 
> void *kmemdup_noprof(const void *src, size_t len, gfp_t gfp)
> {
> 	void *p;
> 
> 	p = kmalloc_node_track_caller_noprof(len, gfp, NUMA_NO_NODE, _RET_IP_);
> 	if (p)
> 		memcpy(p, src, len);
> 	return p;
> }
> 
> Is this sufficiently better?  That's a question for the kernel
> maintainer (cem) and the userspace maintainer (andrey, now cc'd).
> 
> --D

There's still possibility to set wrong length in args->valuelen,
which I suppose what this change tries to prevent.

But otherwise wrapper looks good to me

> 
> > Link: https://lwn.net/Articles/198928/
> > Fixes: 94a69db2367ef ("xfs: use __GFP_NOLOCKDEP instead of GFP_NOFS")
> > Fixes: 384f3ced07efd ("[XFS] Return case-insensitive match for dentry cache")
> > Fixes: 2451337dd0439 ("xfs: global error sign conversion")
> > Cc: Carlos Maiolino <cem at kernel.org>
> > Cc: "Darrick J. Wong" <djwong at kernel.org>
> > Cc: Chandan Babu R <chandanbabu at kernel.org>
> > Cc: Dave Chinner <dchinner at redhat.com>
> > Cc: linux-xfs at vger.kernel.org
> > Cc: linux-kernel at vger.kernel.org
> > Signed-off-by: Mirsad Todorovac <mtodorovac69 at gmail.com>
> > ---
> >  v1:
> > 	initial version.
> > 
> >  fs/xfs/libxfs/xfs_dir2.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/fs/xfs/libxfs/xfs_dir2.c b/fs/xfs/libxfs/xfs_dir2.c
> > index 202468223bf9..24251e42bdeb 100644
> > --- a/fs/xfs/libxfs/xfs_dir2.c
> > +++ b/fs/xfs/libxfs/xfs_dir2.c
> > @@ -379,12 +379,11 @@ xfs_dir_cilookup_result(
> >  					!(args->op_flags & XFS_DA_OP_CILOOKUP))
> >  		return -EEXIST;
> >  
> > -	args->value = kmalloc(len,
> > +	args->value = kmemdup(name, len,
> >  			GFP_KERNEL | __GFP_NOLOCKDEP | __GFP_RETRY_MAYFAIL);
> >  	if (!args->value)
> >  		return -ENOMEM;
> >  
> > -	memcpy(args->value, name, len);
> >  	args->valuelen = len;
> >  	return -EEXIST;
> >  }
> > -- 
> > 2.43.0
> > 
> > 
> 

-- 
- Andrey