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Message-ID: <20240801170838.356177-2-jeffxu@google.com>
Date: Thu, 1 Aug 2024 17:08:33 +0000
From: jeffxu@...omium.org
To: akpm@...ux-foundation.org,
keescook@...omium.org,
jannh@...gle.com,
sroettger@...gle.com,
adhemerval.zanella@...aro.org,
ojeda@...nel.org,
adobriyan@...il.com
Cc: linux-kernel@...r.kernel.org,
linux-mm@...ck.org,
jorgelo@...omium.org,
Jeff Xu <jeffxu@...omium.org>
Subject: [RFC PATCH v1 1/1] binfmt_elf: mseal address zero
From: Jeff Xu <jeffxu@...omium.org>
Some legacy SVr4 apps might depend on page on address zero
to be readable, however I can't find a reason that the page
ever becomes writeable, so seal it.
If there is a compain, we can make this configurable.
Signed-off-by: Jeff Xu <jeffxu@...omium.org>
---
fs/binfmt_elf.c | 4 ++++
include/linux/mm.h | 4 ++++
mm/mseal.c | 2 +-
3 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 19fa49cd9907..e4d35d6f5d65 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1314,6 +1314,10 @@ static int load_elf_binary(struct linux_binprm *bprm)
emulate the SVr4 behavior. Sigh. */
error = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_EXEC,
MAP_FIXED | MAP_PRIVATE, 0);
+
+#ifdef CONFIG_64BIT
+ do_mseal(0, PAGE_SIZE, 0);
+#endif
}
regs = current_pt_regs();
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c4b238a20b76..b5fed60ddcd9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4201,4 +4201,8 @@ void vma_pgtable_walk_end(struct vm_area_struct *vma);
int reserve_mem_find_by_name(const char *name, phys_addr_t *start, phys_addr_t *size);
+#ifdef CONFIG_64BIT
+int do_mseal(unsigned long start, size_t len_in, unsigned long flags);
+#endif
+
#endif /* _LINUX_MM_H */
diff --git a/mm/mseal.c b/mm/mseal.c
index bf783bba8ed0..7a40a84569c8 100644
--- a/mm/mseal.c
+++ b/mm/mseal.c
@@ -248,7 +248,7 @@ static int apply_mm_seal(unsigned long start, unsigned long end)
*
* unseal() is not supported.
*/
-static int do_mseal(unsigned long start, size_t len_in, unsigned long flags)
+int do_mseal(unsigned long start, size_t len_in, unsigned long flags)
{
size_t len;
int ret = 0;
--
2.46.0.rc1.232.g9752f9e123-goog
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