On Fri, Mar 30, 2018 at 04:42:21PM +0800, Simon Glass wrote: > Hi David, > > On 26 March 2018 at 07:25, David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> wrote: > > fdt_string() is used to retrieve strings from a DT blob's strings section. > > It's rarely used directly, but is widely used internally. > > > > However, it doesn't do any bounds checking, which means in the case of a > > corrupted blob it could access bad memory, which libfdt is supposed to > > avoid. > > > > This write a safe alternative to fdt_string, fdt_get_string(). It checks > > both that the given offset is within the string section and that the string > > it points to is properly \0 terminated within the section. It also returns > > the string's length as a convenience (since it needs to determine to do the > > checks anyway). > > > > fdt_string() is rewritten in terms of fdt_get_string() for compatibility. > > > > Most of the diff here is actually testing infrastructure. > > > > Signed-off-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> > > --- > > libfdt/fdt_ro.c | 61 +++++++++++++++++++++++++++++++++++-- > > libfdt/libfdt.h | 18 ++++++++++- > > libfdt/version.lds | 2 +- > > tests/.gitignore | 1 + > > tests/Makefile.tests | 2 +- > > tests/run_tests.sh | 1 + > > tests/testdata.h | 1 + > > tests/testutils.c | 11 +++++-- > > tests/trees.S | 26 ++++++++++++++++ > > tests/truncated_string.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++ > > 10 files changed, 193 insertions(+), 9 deletions(-) > > create mode 100644 tests/truncated_string.c > > Similar code-size quesiton here. It looks like a lot of checking code. > Can we have an option to remove it? Again, I'm disinclined without a concrete example of a problem. Fwiw the code size change is +276 bytes on my setup. > > > > > diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c > > index 4f4ef44..347aa7b 100644 > > --- a/libfdt/fdt_ro.c > > +++ b/libfdt/fdt_ro.c > > @@ -76,17 +76,72 @@ static int fdt_nodename_eq_(const void *fdt, int offset, > > return 0; > > } > > > > +const char *fdt_get_string(const void *fdt, int stroffset, int *lenp) > > Comment? The difference between fdt_get_string() and fdt_string() is > not obvious from the name. There are full banner comments in libfdt.h. Basically the only difference is that fdt_get_string() returns the length as well. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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