Prevent signed underflow by changing loop variables to unsigned and
doing count checks before decrementing. This isn't really a bug, but
prevents UB detected by ubsan on fuzzed input. The bad (fuzzed) input
data does get detected anyway.
* src/readelf.c (handle_verneed): Use unsigned cnt, cnt2.
(handle_verdef): Likewise.
Signed-off-by: Mark Wielaard <m...@klomp.org>
---
src/readelf.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/src/readelf.c b/src/readelf.c
index 802f8ede..0e931184 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -3159,7 +3159,7 @@ handle_verneed (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr)
elf_strptr (ebl->elf, shstrndx, glink->sh_name));
unsigned int offset = 0;
- for (int cnt = shdr->sh_info; --cnt >= 0; )
+ for (unsigned int cnt = shdr->sh_info; cnt > 0; cnt--)
{
/* Get the data at the next offset. */
GElf_Verneed needmem;
@@ -3173,7 +3173,7 @@ handle_verneed (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr)
(unsigned short int) need->vn_cnt);
unsigned int auxoffset = offset + need->vn_aux;
- for (int cnt2 = need->vn_cnt; --cnt2 >= 0; )
+ for (unsigned int cnt2 = need->vn_cnt; cnt2 > 0; cnt2--)
{
GElf_Vernaux auxmem;
GElf_Vernaux *aux = gelf_getvernaux (data, auxoffset, &auxmem);
@@ -3236,7 +3236,7 @@ handle_verdef (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr)
elf_strptr (ebl->elf, shstrndx, glink->sh_name));
unsigned int offset = 0;
- for (int cnt = shdr->sh_info; --cnt >= 0; )
+ for (unsigned int cnt = shdr->sh_info; cnt > 0; cnt--)
{
/* Get the data at the next offset. */
GElf_Verdef defmem;
@@ -3259,7 +3259,7 @@ handle_verdef (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr)
elf_strptr (ebl->elf, shdr->sh_link, aux->vda_name));
auxoffset += aux->vda_next;
- for (int cnt2 = 1; cnt2 < def->vd_cnt; ++cnt2)
+ for (unsigned int cnt2 = 1; cnt2 < def->vd_cnt; ++cnt2)
{
aux = gelf_getverdaux (data, auxoffset, &auxmem);
if (unlikely (aux == NULL))
--
2.39.3
