[PATCH 04/18] mm, aout: handle vm_brk failures

[Michal Hocko]

From: Michal Hocko <mhocko@xxxxxxxx>

vm_brk is allowed to fail but load_aout_binary simply ignores the error
and happily continues. I haven't noticed any problem from that in real
life but later patches will make the failure more likely because
vm_brk will become killable (resp. mmap_sem for write waiting will become
killable) so we should be more careful now.

The error handling should be quite straightforward because there are
calls to vm_mmap which check the error properly already. The only
notable exception is set_brk which is called after beyond_if label.
But nothing indicates that we cannot move it above set_binfmt as the two
do not depend on each other and fail before we do set_binfmt and alter
reference counting.

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
 arch/x86/ia32/ia32_aout.c | 22 +++++++++++++++-------
 fs/binfmt_aout.c          | 11 ++++++++---
 2 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
index ae6aad1d24f7..f5e737ff0022 100644
--- a/arch/x86/ia32/ia32_aout.c
+++ b/arch/x86/ia32/ia32_aout.c
@@ -116,13 +116,13 @@ static struct linux_binfmt aout_format = {
 	.min_coredump	= PAGE_SIZE
 };
 
-static void set_brk(unsigned long start, unsigned long end)
+static unsigned long set_brk(unsigned long start, unsigned long end)
 {
 	start = PAGE_ALIGN(start);
 	end = PAGE_ALIGN(end);
 	if (end <= start)
-		return;
-	vm_brk(start, end - start);
+		return start;
+	return vm_brk(start, end - start);
 }
 
 #ifdef CONFIG_COREDUMP
@@ -349,7 +349,10 @@ static int load_aout_binary(struct linux_binprm *bprm)
 #endif
 
 		if (!bprm->file->f_op->mmap || (fd_offset & ~PAGE_MASK) != 0) {
-			vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
+			error = vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
+			if (IS_ERR_VALUE(error))
+				return error;
+
 			read_code(bprm->file, N_TXTADDR(ex), fd_offset,
 					ex.a_text+ex.a_data);
 			goto beyond_if;
@@ -372,10 +375,13 @@ static int load_aout_binary(struct linux_binprm *bprm)
 		if (error != N_DATADDR(ex))
 			return error;
 	}
+
 beyond_if:
-	set_binfmt(&aout_format);
+	error = set_brk(current->mm->start_brk, current->mm->brk);
+	if (IS_ERR_VALUE(error))
+		return error;
 
-	set_brk(current->mm->start_brk, current->mm->brk);
+	set_binfmt(&aout_format);
 
 	current->mm->start_stack =
 		(unsigned long)create_aout_tables((char __user *)bprm->p, bprm);
@@ -434,7 +440,9 @@ static int load_aout_library(struct file *file)
 			error_time = jiffies;
 		}
 #endif
-		vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
+		retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
+		if (IS_ERR_VALUE(retval))
+			goto out;
 
 		read_code(file, start_addr, N_TXTOFF(ex),
 			  ex.a_text + ex.a_data);
diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
index 4c556680fa74..2fab9f130e51 100644
--- a/fs/binfmt_aout.c
+++ b/fs/binfmt_aout.c
@@ -297,7 +297,10 @@ static int load_aout_binary(struct linux_binprm * bprm)
 		}
 
 		if (!bprm->file->f_op->mmap||((fd_offset & ~PAGE_MASK) != 0)) {
-			vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
+			error = vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
+			if (IS_ERR_VALUE(error))
+				return error;
+
 			read_code(bprm->file, N_TXTADDR(ex), fd_offset,
 				  ex.a_text + ex.a_data);
 			goto beyond_if;
@@ -378,8 +381,10 @@ static int load_aout_library(struct file *file)
 			       "N_TXTOFF is not page aligned. Please convert library: %pD\n",
 			       file);
 		}
-		vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
-		
+		retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
+		if (IS_ERR_VALUE(retval))
+			goto out;
+
 		read_code(file, start_addr, N_TXTOFF(ex),
 			  ex.a_text + ex.a_data);
 		retval = 0;
-- 
2.8.0.rc3