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authorAlexey Dobriyan <adobriyan@gmail.com>2020-01-31 09:17:29 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-01-31 21:30:41 +0300
commit47a2ebb7f5053387f5753b524f4920b9b829f922 (patch)
treeead8bf068e3fc1bedf768953f751c619d2fc93b1 /fs/exec.c
parentaacee5446a2a1aa35d0a49dab289552578657fb4 (diff)
downloadlinux-47a2ebb7f5053387f5753b524f4920b9b829f922.tar.xz
execve: warn if process starts with executable stack
There were few episodes of silent downgrade to an executable stack over years: 1) linking innocent looking assembly file will silently add executable stack if proper linker options is not given as well: $ cat f.S .intel_syntax noprefix .text .globl f f: ret $ cat main.c void f(void); int main(void) { f(); return 0; } $ gcc main.c f.S $ readelf -l ./a.out GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 RWE 0x10 ^^^ 2) converting C99 nested function into a closure https://nullprogram.com/blog/2019/11/15/ void intsort2(int *base, size_t nmemb, _Bool invert) { int cmp(const void *a, const void *b) { int r = *(int *)a - *(int *)b; return invert ? -r : r; } qsort(base, nmemb, sizeof(*base), cmp); } will silently require stack trampolines while non-closure version will not. Without doubt this behaviour is documented somewhere, add a warning so that developers and users can at least notice. After so many years of x86_64 having proper executable stack support it should not cause too many problems. Link: http://lkml.kernel.org/r/20191208171918.GC19716@avx2 Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: Will Deacon <will@kernel.org> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/exec.c')
-rw-r--r--fs/exec.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 74d88dab98dd..7f4e0a89aaa8 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -761,6 +761,11 @@ int setup_arg_pages(struct linux_binprm *bprm,
goto out_unlock;
BUG_ON(prev != vma);
+ if (unlikely(vm_flags & VM_EXEC)) {
+ pr_warn_once("process '%pD4' started with executable stack\n",
+ bprm->file);
+ }
+
/* Move stack pages down in memory. */
if (stack_shift) {
ret = shift_arg_pages(vma, stack_shift);