From 386a26023afb624726fb756ffdbef5b5832caa96 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Tue, 14 Mar 2023 19:17:31 -0400 Subject: Fix corner case bug in numeric to_char() some more. The band-aid applied in commit f0bedf3e4 turns out to still need some work: it made sure we didn't set Np->last_relevant too small (to the left of the decimal point), but it didn't prevent setting it too large (off the end of the partially-converted string). This could result in fetching data beyond the end of the allocated space, which with very bad luck could cause a SIGSEGV, though I don't see any hazard of interesting memory disclosure. Per bug #17839 from Thiago Nunes. The bug's pretty ancient, so back-patch to all supported versions. Discussion: https://postgr.es/m/17839-aada50db24d7b0da@postgresql.org --- src/backend/utils/adt/formatting.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) (limited to 'src/backend/utils/adt/formatting.c') diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c index f1a753fc91c..e4ffecb9d85 100644 --- a/src/backend/utils/adt/formatting.c +++ b/src/backend/utils/adt/formatting.c @@ -5685,13 +5685,20 @@ NUM_processor(FormatNode *node, NUMDesc *Num, char *inout, /* * If any '0' specifiers are present, make sure we don't strip - * those digits. + * those digits. But don't advance last_relevant beyond the last + * character of the Np->number string, which is a hazard if the + * number got shortened due to precision limitations. */ if (Np->last_relevant && Np->Num->zero_end > Np->out_pre_spaces) { + int last_zero_pos; char *last_zero; - last_zero = Np->number + (Np->Num->zero_end - Np->out_pre_spaces); + /* note that Np->number cannot be zero-length here */ + last_zero_pos = strlen(Np->number) - 1; + last_zero_pos = Min(last_zero_pos, + Np->Num->zero_end - Np->out_pre_spaces); + last_zero = Np->number + last_zero_pos; if (Np->last_relevant < last_zero) Np->last_relevant = last_zero; } -- cgit v1.2.3