Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 1 Feb 2018 14:48:29 +0100
From:   Michal Hocko <mhocko@kernel.org>
To:     Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc:     Michael Ellerman <mpe@ellerman.id.au>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        mm-commits@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        linux-next@vger.kernel.org, sfr@canb.auug.org.au,
        broonie@kernel.org
Subject: Re: ppc elf_map breakage with MAP_FIXED_NOREPLACE
Message-ID: <20180201134829.GL21609@dhcp22.suse.cz>
References: <5acba3c2-754d-e449-24ff-a72a0ad0d895@linux.vnet.ibm.com>
 <20180126140415.GD5027@dhcp22.suse.cz>
 <15da8c87-e6db-13aa-01c8-a913656bfdb6@linux.vnet.ibm.com>
 <6db9b33d-fd46-c529-b357-3397926f0733@linux.vnet.ibm.com>
 <20180129132235.GE21609@dhcp22.suse.cz>
 <87k1w081e7.fsf@concordia.ellerman.id.au>
 <20180130094205.GS21609@dhcp22.suse.cz>
 <5eccdc1b-6a10-b48a-c63f-295f69473d97@linux.vnet.ibm.com>
 <20180131131937.GA6740@dhcp22.suse.cz>
 <bfecda5e-ae8b-df91-0add-df6322b42a70@linux.vnet.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <bfecda5e-ae8b-df91-0add-df6322b42a70@linux.vnet.ibm.com>
User-Agent: Mutt/1.9.2 (2017-12-15)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu 01-02-18 08:43:34, Anshuman Khandual wrote:
[...]
> $dmesg | grep elf_brk
> [    9.571192] elf_brk 10030328 elf_bss 10030000
> 
> static int load_elf_binary(struct linux_binprm *bprm)
> ---------------------
> 
> 	if (unlikely (elf_brk > elf_bss)) {
> 			unsigned long nbyte;
> 	            
> 			/* There was a PT_LOAD segment with p_memsz > p_filesz
> 			   before this one. Map anonymous pages, if needed,
> 			   and clear the area.  */
> 			retval = set_brk(elf_bss + load_bias,
> 					 elf_brk + load_bias,
> 					 bss_prot);
> 
> 
> ---------------------

Just a blind shot... Does the following make any difference?
---
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 021fe78998ea..04b24d00c911 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -895,7 +895,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	   the correct location in memory. */
 	for(i = 0, elf_ppnt = elf_phdata;
 	    i < loc->elf_ex.e_phnum; i++, elf_ppnt++) {
-		int elf_prot = 0, elf_flags;
+		int elf_prot = 0, elf_flags, elf_fixed = MAP_FIXED_NOREPLACE;
 		unsigned long k, vaddr;
 		unsigned long total_size = 0;
 
@@ -927,6 +927,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 					 */
 				}
 			}
+			elf_fixed = MAP_FIXED;
 		}
 
 		if (elf_ppnt->p_flags & PF_R)
@@ -944,7 +945,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 		 * the ET_DYN load_addr calculations, proceed normally.
 		 */
 		if (loc->elf_ex.e_type == ET_EXEC || load_addr_set) {
-			elf_flags |= MAP_FIXED_NOREPLACE;
+			elf_flags |= elf_fixed;
 		} else if (loc->elf_ex.e_type == ET_DYN) {
 			/*
 			 * This logic is run once for the first LOAD Program
@@ -980,7 +981,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 				load_bias = ELF_ET_DYN_BASE;
 				if (current->flags & PF_RANDOMIZE)
 					load_bias += arch_mmap_rnd();
-				elf_flags |= MAP_FIXED_NOREPLACE;
+				elf_flags |= elf_fixed;
 			} else
 				load_bias = 0;
 

-- 
Michal Hocko
SUSE Labs