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authorKees Cook <keescook@chromium.org>2024-02-17 07:25:44 +0100
committerKees Cook <keescook@chromium.org>2024-04-24 21:20:35 +0200
commit2a5eb9995528441447d33838727f6ec1caf08139 (patch)
tree1d19fdfcfa64b5c240fcb35a24dab852c9490c80 /fs/binfmt_elf.c
parentReplace macro "ARCH_HAVE_EXTRA_ELF_NOTES" with kconfig (diff)
downloadlinux-2a5eb9995528441447d33838727f6ec1caf08139.tar.xz
linux-2a5eb9995528441447d33838727f6ec1caf08139.zip
binfmt_elf: Leave a gap between .bss and brk
Currently the brk starts its randomization immediately after .bss, which means there is a chance that when the random offset is 0, linear overflows from .bss can reach into the brk area. Leave at least a single page gap between .bss and brk (when it has not already been explicitly relocated into the mmap range). Reported-by: <y0un9n132@gmail.com> Closes: https://lore.kernel.org/linux-hardening/CA+2EKTVLvc8hDZc+2Yhwmus=dzOUG5E4gV7ayCbu0MPJTZzWkw@mail.gmail.com/ Link: https://lore.kernel.org/r/20240217062545.1631668-2-keescook@chromium.org Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'fs/binfmt_elf.c')
-rw-r--r--fs/binfmt_elf.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 5397b552fbeb..7862962f7a85 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1262,6 +1262,9 @@ out_free_interp:
if (IS_ENABLED(CONFIG_ARCH_HAS_ELF_RANDOMIZE) &&
elf_ex->e_type == ET_DYN && !interpreter) {
mm->brk = mm->start_brk = ELF_ET_DYN_BASE;
+ } else {
+ /* Otherwise leave a gap between .bss and brk. */
+ mm->brk = mm->start_brk = mm->brk + PAGE_SIZE;
}
mm->brk = mm->start_brk = arch_randomize_brk(mm);