linux-kernel - [PATCH v3 2/2] fs: clear a UBSAN shift-out-of-bounds warning

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Date:   Fri, 25 Nov 2022 17:13:58 +0800
From:   Zhen Lei <thunder.leizhen@...wei.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Eric Biggers <ebiggers@...nel.org>,
        <linux-fsdevel@...r.kernel.org>, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>, <linux-btrfs@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Zhen Lei <thunder.leizhen@...wei.com>
Subject: [PATCH v3 2/2] fs: clear a UBSAN shift-out-of-bounds warning

UBSAN: shift-out-of-bounds in fs/locks.c:2572:16
left shift of 1 by 63 places cannot be represented in type 'long long 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
 locks_remove_posix+0xba/0x290 fs/locks.c:2572
 filp_close+0x61/0xa0 fs/open.c:1424
 close_fd+0x56/0x70 fs/file.c:664
 __do_sys_close fs/open.c:1439 [inline]
 __se_sys_close fs/open.c:1437 [inline]
 __x64_sys_close+0x1a/0x50 fs/open.c:1437
 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
</TASK>

INT_LIMIT() tries to do what type_max() does, except that type_max()
doesn't rely upon undefined behaviour, might as well use type_max()
instead.

Suggested-by: Eric Biggers <ebiggers@...nel.org>
Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
Reviewed-by: Eric Biggers <ebiggers@...gle.com>
---
 include/linux/fs.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index e654435f16512c1..a384741b1449457 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1131,9 +1131,8 @@ struct file_lock_context {
 
 /* The following constant reflects the upper bound of the file/locking space */
 #ifndef OFFSET_MAX
-#define INT_LIMIT(x)	(~((x)1 << (sizeof(x)*8 - 1)))
-#define OFFSET_MAX	INT_LIMIT(loff_t)
-#define OFFT_OFFSET_MAX	INT_LIMIT(off_t)
+#define OFFSET_MAX	type_max(loff_t)
+#define OFFT_OFFSET_MAX	type_max(off_t)
 #endif
 
 extern void send_sigio(struct fown_struct *fown, int fd, int band);
-- 
2.25.1