[Linux-kernel-mentees] [PATCH] checkpatch: add a new check for strcpy/strlcpy uses
David.Laight at ACULAB.COM
Tue Jan 5 10:20:07 UTC 2021
From: Joe Perches
> Sent: 05 January 2021 08:44
> On Tue, 2021-01-05 at 13:53 +0530, Dwaipayan Ray wrote:
> > strcpy() performs no bounds checking on the destination buffer.
> > This could result in linear overflows beyond the end of the buffer.
> > strlcpy() reads the entire source buffer first. This read
> > may exceed the destination size limit. This can be both inefficient
> > and lead to linear read overflows.
> > The safe replacement to both of these is to use strscpy() instead.
> > Add a new checkpatch warning which alerts the user on finding usage of
> > strcpy() or strlcpy().
> I do not believe that strscpy is preferred over strcpy.
> When the size of the output buffer is known to be larger
> than the input, strcpy is faster.
> There are about 2k uses of strcpy.
> Is there a use where strcpy use actually matters?
> I don't know offhand...
> But I believe compilers do not optimize away the uses of strscpy
> to a simple memcpy like they do for strcpy with a const from
> strcpy(foo, "bar");
It ought to be possible to convert:
strscpy(foo, "bar", constant_sz)
to a memcpy() within the .h file.
Similarly it should be possible to error
Unless foo is large enough and "bar" is constant.
After all with a length check
is actually safer than
strspy(foo, "bar", sizeof foo)
because there is less room for error.
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
More information about the Linux-kernel-mentees