linux-ext4 - [PATCH] ext4: fix undefined behavior in bit shift for ext4_check_flag

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Date:   Mon, 31 Oct 2022 13:58:33 +0800
From:   Gaosheng Cui <cuigaosheng1@...wei.com>
To:     <tytso@....edu>, <adilger.kernel@...ger.ca>,
        <cmaiolino@...hat.com>, <cuigaosheng1@...wei.com>
CC:     <linux-ext4@...r.kernel.org>
Subject: [PATCH] ext4: fix undefined behavior in bit shift for ext4_check_flag_values

Shifting signed 32-bit value by 31 bits is undefined, so changing
significant bit to unsigned. The UBSAN warning calltrace like below:

UBSAN: shift-out-of-bounds in fs/ext4/ext4.h:591:2
left shift of 1 by 31 places cannot be represented in type 'int'
Call Trace:
 <TASK>
 dump_stack_lvl+0x7d/0xa5
 dump_stack+0x15/0x1b
 ubsan_epilogue+0xe/0x4e
 __ubsan_handle_shift_out_of_bounds+0x1e7/0x20c
 ext4_init_fs+0x5a/0x277
 do_one_initcall+0x76/0x430
 kernel_init_freeable+0x3b3/0x422
 kernel_init+0x24/0x1e0
 ret_from_fork+0x1f/0x30
 </TASK>

Fixes: 9a4c80194713 ("ext4: ensure Inode flags consistency are checked at build time")
Signed-off-by: Gaosheng Cui <cuigaosheng1@...wei.com>
---
 fs/ext4/ext4.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 8d5453852f98..e2d12e6c998d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -558,7 +558,7 @@ enum {
  *
  * It's not paranoia if the Murphy's Law really *is* out to get you.  :-)
  */
-#define TEST_FLAG_VALUE(FLAG) (EXT4_##FLAG##_FL == (1 << EXT4_INODE_##FLAG))
+#define TEST_FLAG_VALUE(FLAG) (EXT4_##FLAG##_FL == (1U << EXT4_INODE_##FLAG))
 #define CHECK_FLAG_VALUE(FLAG) BUILD_BUG_ON(!TEST_FLAG_VALUE(FLAG))
 
 static inline void ext4_check_flag_values(void)
-- 
2.25.1