4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Max Filippov <jcmvbkbc@xxxxxxxxx>
commit 2aea94ac14d1e0a8ae9e34febebe208213ba72f7 upstream.
In NOMMU kernel the value of linux_binprm::p is the offset inside the
temporary program arguments array maintained in separate pages in the
linux_binprm::page. linux_binprm::exec being a copy of linux_binprm::p
thus must be adjusted when that array is copied to the user stack.
Without that adjustment the value passed by the NOMMU kernel to the ELF
program in the AT_EXECFN entry of the aux array doesn't make any sense
and it may break programs that try to access memory pointed to by that
entry.
Adjust linux_binprm::exec before the successful return from the
transfer_args_to_stack().
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: b6a2fea39318 ("mm: variable length argument support")
Fixes: 5edc2a5123a7 ("binfmt_elf_fdpic: wire up AT_EXECFD, AT_EXECFN, AT_SECURE")
Signed-off-by: Max Filippov <jcmvbkbc@xxxxxxxxx>
Link: https://lore.kernel.org/r/20240320182607.1472887-1-jcmvbkbc@xxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/exec.c | 1 +
1 file changed, 1 insertion(+)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -823,6 +823,7 @@ int transfer_args_to_stack(struct linux_
goto out;
}
+ bprm->exec += *sp_location - MAX_ARG_PAGES * PAGE_SIZE;
*sp_location = sp;
out:
