@@ -2362,31 +2362,58 @@ static abi_ulong setup_arg_pages(struct linux_binprm *bprm,
* Map and zero the bss. We need to explicitly zero any fractional pages
* after the data section (i.e. bss). Return false on mapping failure.
*/
-static bool zero_bss(abi_ulong start_bss, abi_ulong end_bss, int prot)
+static bool zero_bss(abi_ulong start_bss, abi_ulong end_bss,
+ int prot, Error **errp)
{
abi_ulong align_bss;
+ /* We only expect writable bss; the code segment shouldn't need this. */
+ if (!(prot & PROT_WRITE)) {
+ error_setg(errp, "PT_LOAD with non-writable bss");
+ return false;
+ }
+
align_bss = TARGET_PAGE_ALIGN(start_bss);
end_bss = TARGET_PAGE_ALIGN(end_bss);
if (start_bss < align_bss) {
int flags = page_get_flags(start_bss);
- if (!(flags & PAGE_VALID)) {
- /* Map the start of the bss. */
+ if (!(flags & PAGE_BITS)) {
+ /*
+ * The whole address space of the executable was reserved
+ * at the start, therefore all pages will be VALID.
+ * But assuming there are no PROT_NONE PT_LOAD segments,
+ * a PROT_NONE page means no data all bss, and we can
+ * simply extend the new anon mapping back to the start
+ * of the page of bss.
+ */
align_bss -= TARGET_PAGE_SIZE;
- } else if (flags & PAGE_WRITE) {
- /* The page is already mapped writable. */
- memset(g2h_untagged(start_bss), 0, align_bss - start_bss);
} else {
- /* Read-only zeros? */
- g_assert_not_reached();
+ /*
+ * The start of the bss shares a page with something.
+ * The only thing that we expect is the data section,
+ * which would already be marked writable.
+ * Overlapping the RX code segment seems malformed.
+ */
+ if (!(flags & PAGE_WRITE)) {
+ error_setg(errp, "PT_LOAD with bss overlapping "
+ "non-writable page");
+ return false;
+ }
+
+ /* The page is already mapped and writable. */
+ memset(g2h_untagged(start_bss), 0, align_bss - start_bss);
}
}
- return align_bss >= end_bss ||
- target_mmap(align_bss, end_bss - align_bss, prot,
- MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1, 0) != -1;
+ if (align_bss < end_bss &&
+ target_mmap(align_bss, end_bss - align_bss, prot,
+ MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1, 0) == -1) {
+ error_setg_errno(errp, errno, "Error mapping bss");
+ return false;
+ }
+ return true;
}
#if defined(TARGET_ARM)
@@ -3410,8 +3437,8 @@ static void load_elf_image(const char *image_name, int image_fd,
/* If the load segment requests extra zeros (e.g. bss), map it. */
if (vaddr_ef < vaddr_em &&
- !zero_bss(vaddr_ef, vaddr_em, elf_prot)) {
- goto exit_mmap;
+ !zero_bss(vaddr_ef, vaddr_em, elf_prot, &err)) {
+ goto exit_errmsg;
}
/* Find the full program boundaries. */
The previous change, 2d385be6152, assumed !PAGE_VALID meant that the page would be unmapped by the elf image. However, since we reserved the entire image space via mmap, PAGE_VALID will always be set. Instead, assume PROT_NONE for the same condition. Furthermore, assume bss is only ever present for writable segments, and that there is no page overlap between PT_LOAD segments. Instead of an assert, return false to indicate failure. Cc: qemu-stable@nongnu.org Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1854 Fixes: 2d385be6152 ("linux-user: Do not adjust zero_bss for host page size") Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- linux-user/elfload.c | 53 +++++++++++++++++++++++++++++++++----------- 1 file changed, 40 insertions(+), 13 deletions(-)