diff options
author | Richard Henderson <richard.henderson@linaro.org> | 2023-08-30 13:33:54 -0700 |
---|---|---|
committer | Richard Henderson <richard.henderson@linaro.org> | 2023-10-18 15:32:16 -0700 |
commit | e6e66b03287331abc6f184456dbc6d25505590ec (patch) | |
tree | 39bcf5f9f0af8f4e3a3f1eab514d1ecd30b2d5f3 /linux-user/elfload.c | |
parent | ec6f9f135d5e5596ab0258da2ddd048f1fd8c359 (diff) |
linux-user: Fixes for zero_bss
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>
Diffstat (limited to 'linux-user/elfload.c')
-rw-r--r-- | linux-user/elfload.c | 53 |
1 files changed, 40 insertions, 13 deletions
diff --git a/linux-user/elfload.c b/linux-user/elfload.c index f21e2e0c3d..213fd3e584 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -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. */ |