linux-kernel - [RFC PATCH 6/6] sys_sparc_64.c: Check length of unmapped area before allowing MAP

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Date:   Mon, 6 Dec 2021 15:02:54 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Liam Howlett <liam.howlett@...cle.com>,
        "David S. Miller" <davem@...emloft.net>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 6/6] sys_sparc_64.c: Check length of unmapped area before
 allowing MAP_FIXED

arch_get_unmapped_area() and arch_get_unmapped_area_topdown() could
potentially allow a larger than possible length when using the MAP_FIXED
flag.  The bound check should come before the check for MAP_FIXED.

Fixes: ca56c8ee6fa0 (v2.4.3.2 -> v2.4.3.3)
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 arch/sparc/kernel/sys_sparc_64.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/sparc/kernel/sys_sparc_64.c b/arch/sparc/kernel/sys_sparc_64.c
index 1e9a9e016237..4ca7f9c18c54 100644
--- a/arch/sparc/kernel/sys_sparc_64.c
+++ b/arch/sparc/kernel/sys_sparc_64.c
@@ -95,6 +95,11 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsi
 	int do_color_align;
 	struct vm_unmapped_area_info info;
 
+	if (test_thread_flag(TIF_32BIT))
+		task_size = STACK_TOP32;
+	if (unlikely(len > task_size || len >= VA_EXCLUDE_START))
+		return -ENOMEM;
+
 	if (flags & MAP_FIXED) {
 		/* We do not accept a shared mapping if it would violate
 		 * cache aliasing constraints.
@@ -105,11 +110,6 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsi
 		return addr;
 	}
 
-	if (test_thread_flag(TIF_32BIT))
-		task_size = STACK_TOP32;
-	if (unlikely(len > task_size || len >= VA_EXCLUDE_START))
-		return -ENOMEM;
-
 	do_color_align = 0;
 	if (filp || (flags & MAP_SHARED))
 		do_color_align = 1;
@@ -159,6 +159,9 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 	/* This should only ever run for 32-bit processes.  */
 	BUG_ON(!test_thread_flag(TIF_32BIT));
 
+	if (unlikely(len > task_size))
+		return -ENOMEM;
+
 	if (flags & MAP_FIXED) {
 		/* We do not accept a shared mapping if it would violate
 		 * cache aliasing constraints.
@@ -169,9 +172,6 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 		return addr;
 	}
 
-	if (unlikely(len > task_size))
-		return -ENOMEM;
-
 	do_color_align = 0;
 	if (filp || (flags & MAP_SHARED))
 		do_color_align = 1;
-- 
2.30.2