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Date: Sun, 30 Aug 2020 11:13:53 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: Alex Dewar <alex.dewar90@...il.com> Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Christian Brauner <christian.brauner@...ntu.com>, "David S. Miller" <davem@...emloft.net>, Nayna Jain <nayna@...ux.ibm.com>, Dan Williams <dan.j.williams@...el.com>, Mauro Carvalho Chehab <mchehab+huawei@...nel.org>, Sourabh Jain <sourabhjain@...ux.ibm.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH RFC 2/2] sysfs: add helper macro for showing simple integer values On Sun, Aug 30, 2020 at 12:37:17AM +0100, Alex Dewar wrote: > sysfs attributes are supposed to be only single values, which are > printed into a buffer of PAGE_SIZE. Accordingly, for many simple > attributes, sprintf() can be used like so: > static ssize_t my_show(..., char *buf) > { > ... > return sprintf("%d\n", my_integer); > } > > The problem is that whilst this use of sprintf() is memory safe, other > cases where e.g. a possibly unterminated string is passed as input, are > not and so use of sprintf() here might make it more difficult to > identify these problematic cases. > > Define a macro, sysfs_sprinti(), which outputs the value of a single > integer to a buffer (with terminating "\n\0") and returns the size written. > This way, we can convert over the some of the trivially correct users of > sprintf() and decrease its usage in the kernel source tree. > > Another advantage of this approach is that we can now statically check > the type of the integer so that e.g. an unsigned long long will be > formatted as %llu. This will fix cases where the wrong format string has > been passed to sprintf(). > > Signed-off-by: Alex Dewar <alex.dewar90@...il.com> > --- > include/linux/sysfs.h | 31 +++++++++++++++++++++++++++++++ > 1 file changed, 31 insertions(+) Did you try this out? Don't you need to return the number of bytes written? I like Joe's patches better, this feels like more work... thanks, greg k-h
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