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[for,4.4,4.9] binfmt_elf: Do not move brk for INTERP-less ET_EXEC

Message ID 20200513085932.920902-1-nobuhiro1.iwamatsu@toshiba.co.jp
State New
Headers show
Series [for,4.4,4.9] binfmt_elf: Do not move brk for INTERP-less ET_EXEC | expand

Commit Message

Nobuhiro Iwamatsu May 13, 2020, 8:59 a.m. UTC 
From: Kees Cook <keescook@chromium.org>

commit 7be3cb019db1cbd5fd5ffe6d64a23fefa4b6f229 upstream.

When brk was moved for binaries without an interpreter, it should have
been limited to ET_DYN only. In other words, the special case was an
ET_DYN that lacks an INTERP, not just an executable that lacks INTERP.
The bug manifested for giant static executables, where the brk would end
up in the middle of the text area on 32-bit architectures.

Reported-and-tested-by: Richard Kojedzinszky <richard@kojedz.in>
Fixes: bbdc6076d2e5 ("binfmt_elf: move brk out of mmap when doing direct loader exec")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
---
 fs/binfmt_elf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
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Patch

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index a6857e9bd4460..164e5fedd7b6a 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1104,7 +1104,8 @@  static int load_elf_binary(struct linux_binprm *bprm)
 		 * (since it grows up, and may collide early with the stack
 		 * growing down), and into the unused ELF_ET_DYN_BASE region.
 		 */
-		if (IS_ENABLED(CONFIG_ARCH_HAS_ELF_RANDOMIZE) && !interpreter)
+		if (IS_ENABLED(CONFIG_ARCH_HAS_ELF_RANDOMIZE) &&
+		    loc->elf_ex.e_type == ET_DYN && !interpreter)
 			current->mm->brk = current->mm->start_brk =
 				ELF_ET_DYN_BASE;