[patch 07/11] fs, elf: make sure to page align bss in load_elf_library

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From: Oscar Salvador <osalvador@xxxxxxx>
Subject: fs, elf: make sure to page align bss in load_elf_library

The current code does not make sure to page align bss before calling
vm_brk(), and this can lead to a VM_BUG_ON() in __mm_populate()
due to the requested lenght not being correctly aligned.

Let us make sure to align it properly.

Kees: only applicable to CONFIG_USELIB kernels: 32-bit and configured for
libc5.

Link: http://lkml.kernel.org/r/20180705145539.9627-1-osalvador@xxxxxxxxxxxxxxxxxx
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
Reported-by: syzbot+5dcb560fe12aa5091c06@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Nicolas Pitre <nicolas.pitre@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 fs/binfmt_elf.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff -puN fs/binfmt_elf.c~fs-elf-make-sure-to-page-align-bss-in-load_elf_library fs/binfmt_elf.c
--- a/fs/binfmt_elf.c~fs-elf-make-sure-to-page-align-bss-in-load_elf_library
+++ a/fs/binfmt_elf.c
@@ -1259,9 +1259,8 @@ static int load_elf_library(struct file
 		goto out_free_ph;
 	}
 
-	len = ELF_PAGESTART(eppnt->p_filesz + eppnt->p_vaddr +
-			    ELF_MIN_ALIGN - 1);
-	bss = eppnt->p_memsz + eppnt->p_vaddr;
+	len = ELF_PAGEALIGN(eppnt->p_filesz + eppnt->p_vaddr);
+	bss = ELF_PAGEALIGN(eppnt->p_memsz + eppnt->p_vaddr);
 	if (bss > len) {
 		error = vm_brk(len, bss - len);
 		if (error)
_



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