metag: Reduce maximum stack size to 256MB

Specify the maximum stack size for arches where the stack grows upward (parisc and metag) in asm/processor.h rather than hard coding in fs/exec.c so that metag can specify a smaller value of 256MB rather than 1GB. This fixes a BUG on metag if the RLIMIT_STACK hard limit is increased beyond a safe value by root. E.g. when starting a process after running "ulimit -H -s unlimited" it will then attempt to use a stack size of the maximum 1GB which is far too big for metag's limited user virtual address space (stack_top is usually 0x3ffff000): BUG: failure at fs/exec.c:589/shift_arg_pages()! Signed-off-by: James Hogan <[email protected]> Cc: Helge Deller <[email protected]> Cc: "James E.J. Bottomley" <[email protected]> Cc: [email protected] Cc: [email protected] Cc: John David Anglin <[email protected]> Cc: [email protected] # only needed for >= v3.9 (arch/metag)
tdeneau · May 14, 2014 · d71f290 · d71f290
1 parent 2425ce8
commit d71f290
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Showing 3 changed files with 7 additions and 3 deletions.
diff --git a/arch/metag/include/asm/processor.h b/arch/metag/include/asm/processor.h
@@ -22,6 +22,8 @@
 /* Add an extra page of padding at the top of the stack for the guard page. */
 #define STACK_TOP	(TASK_SIZE - PAGE_SIZE)
 #define STACK_TOP_MAX	STACK_TOP
+/* Maximum virtual space for stack */
+#define STACK_SIZE_MAX	(1 << 28)	/* 256 MB */
 
 /* This decides where the kernel will search for a free chunk of vm
  * space during mmap's.

diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/processor.h
@@ -55,6 +55,8 @@
 #define STACK_TOP	TASK_SIZE
 #define STACK_TOP_MAX	DEFAULT_TASK_SIZE
 
+#define STACK_SIZE_MAX	(1 << 30)	/* 1 GB */
+
 #endif
 
 #ifndef __ASSEMBLY__

diff --git a/fs/exec.c b/fs/exec.c
@@ -657,10 +657,10 @@ int setup_arg_pages(struct linux_binprm *bprm,
 	unsigned long rlim_stack;
 
 #ifdef CONFIG_STACK_GROWSUP
-	/* Limit stack size to 1GB */
+	/* Limit stack size */
 	stack_base = rlimit_max(RLIMIT_STACK);
-	if (stack_base > (1 << 30))
-		stack_base = 1 << 30;
+	if (stack_base > STACK_SIZE_MAX)
+		stack_base = STACK_SIZE_MAX;
 
 	/* Make sure we didn't let the argument array grow too large. */
 	if (vma->vm_end - vma->vm_start > stack_base)