Le 05/02/2017 à 00:05, Peter Maydell a écrit :
> Coverity doesn't like the code in load_symbols() which assumes
> it can use 'int' for a variable that might hold an offset into
> the guest ELF file, because in a 64-bit guest that could
> overflow. Guest binaries with 2GB sections aren't very likely
> and this isn't a security issue because we fully trust the
> guest linux-user binary anyway, but we might as well use the
> right types, which will placate Coverity. Use uint64_t to
> hold section sizes, and bail out if the symbol table is too
> large rather than just overflowing an int.
>
> (Coverity issue CID1005776)
>
> Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
Reviewed-by: Laurent Vivier <laur...@vivier.eu>
> ---
> linux-user/elfload.c | 22 +++++++++++++++-------
> 1 file changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index c66cbbe..f4c7b0c 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -2263,6 +2263,7 @@ static int symcmp(const void *s0, const void *s1)
> static void load_symbols(struct elfhdr *hdr, int fd, abi_ulong load_bias)
> {
> int i, shnum, nsyms, sym_idx = 0, str_idx = 0;
> + uint64_t segsz;
> struct elf_shdr *shdr;
> char *strings = NULL;
> struct syminfo *s = NULL;
> @@ -2294,19 +2295,26 @@ static void load_symbols(struct elfhdr *hdr, int fd,
> abi_ulong load_bias)
> goto give_up;
> }
>
> - i = shdr[str_idx].sh_size;
> - s->disas_strtab = strings = g_try_malloc(i);
> - if (!strings || pread(fd, strings, i, shdr[str_idx].sh_offset) != i) {
> + segsz = shdr[str_idx].sh_size;
> + s->disas_strtab = strings = g_try_malloc(segsz);
> + if (!strings ||
> + pread(fd, strings, segsz, shdr[str_idx].sh_offset) != segsz) {
> goto give_up;
> }
>
> - i = shdr[sym_idx].sh_size;
> - syms = g_try_malloc(i);
> - if (!syms || pread(fd, syms, i, shdr[sym_idx].sh_offset) != i) {
> + segsz = shdr[sym_idx].sh_size;
> + syms = g_try_malloc(segsz);
> + if (!syms || pread(fd, syms, segsz, shdr[sym_idx].sh_offset) != segsz) {
> goto give_up;
> }
>
> - nsyms = i / sizeof(struct elf_sym);
> + if (segsz / sizeof(struct elf_sym) > INT_MAX) {
> + /* Implausibly large symbol table: give up rather than ploughing
> + * on with the number of symbols calculation overflowing
> + */
> + goto give_up;
> + }
> + nsyms = segsz / sizeof(struct elf_sym);
> for (i = 0; i < nsyms; ) {
> bswap_sym(syms + i);
> /* Throw away entries which we do not need. */
>
