Hi Matthias, On Thu, 25 Mar 2021 at 16:38, Matthias Brugger <matthias....@gmail.com> wrote: > > > > On 25/03/2021 01:38, Simon Glass wrote: > > Hi Matthias, > > > > On Thu, 18 Mar 2021 at 00:30, <matthias....@kernel.org> wrote: > >> > >> From: Matthias Brugger <mbrug...@suse.com> > >> > >> When no string is present in a table, next_ptr points to the same > >> location as eos. When calculating the string table length, we would only > >> reserve one \0. By spec a SMBIOS table has to end with two \0\0 when no > >> strings a present. > >> > >> Signed-off-by: Matthias Brugger <mbrug...@suse.com> > >> > >> --- > >> > >> lib/smbios.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > > > > There is a bug here but I don't think this is right fix. I remember > > worrying about this, making the same change as you did, reverting it > > and then forgetting about it :-( It has no tests. > > > > You are effectively changing the definition of next_ptr here: > > > > * @next_ptr: pointer to the start of the next string to be added. When the > > * table is not empty, this points to the byte after the \0 of the > > * previous string. > > > > That's true. > > > (there is a typo in that in the code) > > > > I think that breaks adding new strings. > > > > Well it doesn't because when adding a new string, ctx->next_ptr gets > overwritten > [1]. It is only used to calculate the lenght of the string in > smbios_string_table_len() to calculate the size of the table [2]. But yes it's > not the obvious way to handle the case when no string is present. > > > Can you instead change smbios_string_table_len() to add 2? > > > > Do you mean returning 2 when no string is present (ctx->next_ptr == ctx->eos)? > > Adding 2 will break the case when we have a string present, as a string > already > finishes with '\0' and we only need a second '\0'.
Oh dear, this is complicated. I think we need to add a few unit tests. Do you have time to try that? Regards, Simon > > Regards, > Matthias > > [1] https://source.denx.de/u-boot/u-boot/-/blob/master/lib/smbios.c#L95 > [2] https://source.denx.de/u-boot/u-boot/-/blob/master/lib/smbios.c#L196 > > >> > >> diff --git a/lib/smbios.c b/lib/smbios.c > >> index 7d463c84a9..d21d37cdac 100644 > >> --- a/lib/smbios.c > >> +++ b/lib/smbios.c > >> @@ -153,7 +153,7 @@ static int smbios_add_prop(struct smbios_ctx *ctx, > >> const char *prop) > >> static void smbios_set_eos(struct smbios_ctx *ctx, char *eos) > >> { > >> ctx->eos = eos; > >> - ctx->next_ptr = eos; > >> + ctx->next_ptr = eos + 1; > >> ctx->last_str = NULL; > >> } > >> > >> -- > >> 2.30.2 > >> > > > > Regards, > > Simon > >