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| author | Kees Cook <keescook@chromium.org> | 2024-02-16 22:25:44 -0800 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2024-04-24 12:20:35 -0700 |
| commit | 2a5eb9995528441447d33838727f6ec1caf08139 (patch) | |
| tree | 1d19fdfcfa64b5c240fcb35a24dab852c9490c80 | |
| parent | a9c3475dd67bd828d999e95d0ba985e7ac4cbbb7 (diff) | |
| download | linux-2a5eb9995528441447d33838727f6ec1caf08139.tar.gz linux-2a5eb9995528441447d33838727f6ec1caf08139.tar.bz2 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>
| -rw-r--r-- | fs/binfmt_elf.c | 3 |
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); |