[PATCH AUTOSEL 4.14] binfmt_misc: fix shift-out-of-bounds in check_special_flags

From: Sasha Levin
Date: Mon Jan 16 2023 - 09:18:24 EST


From: Liu Shixin <liushixin2@xxxxxxxxxx>

[ Upstream commit 6a46bf558803dd2b959ca7435a5c143efe837217 ]

UBSAN reported a shift-out-of-bounds warning:

left shift of 1 by 31 places cannot be represented in type 'int'
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x8d/0xcf lib/dump_stack.c:106
ubsan_epilogue+0xa/0x44 lib/ubsan.c:151
__ubsan_handle_shift_out_of_bounds+0x1e7/0x208 lib/ubsan.c:322
check_special_flags fs/binfmt_misc.c:241 [inline]
create_entry fs/binfmt_misc.c:456 [inline]
bm_register_write+0x9d3/0xa20 fs/binfmt_misc.c:654
vfs_write+0x11e/0x580 fs/read_write.c:582
ksys_write+0xcf/0x120 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x34/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x4194e1

Since the type of Node's flags is unsigned long, we should define these
macros with same type too.

Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221102025123.1117184-1-liushixin2@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/binfmt_misc.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 566296ce7ea8..c19bf5c2fbec 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -42,10 +42,10 @@ static LIST_HEAD(entries);
static int enabled = 1;

enum {Enabled, Magic};
-#define MISC_FMT_PRESERVE_ARGV0 (1 << 31)
-#define MISC_FMT_OPEN_BINARY (1 << 30)
-#define MISC_FMT_CREDENTIALS (1 << 29)
-#define MISC_FMT_OPEN_FILE (1 << 28)
+#define MISC_FMT_PRESERVE_ARGV0 (1UL << 31)
+#define MISC_FMT_OPEN_BINARY (1UL << 30)
+#define MISC_FMT_CREDENTIALS (1UL << 29)
+#define MISC_FMT_OPEN_FILE (1UL << 28)

typedef struct {
struct list_head list;
--
2.35.1