* [PATCH] fs: Avoid signed overflow UBSAN warning
@ 2019-02-23 9:02 Hongbo Yao
2019-03-05 4:26 ` Matthew Wilcox
0 siblings, 1 reply; 2+ messages in thread
From: Hongbo Yao @ 2019-02-23 9:02 UTC (permalink / raw)
To: viro, linux-fsdevel, linux-kernel, linuxarm
I ran into this:
UBSAN: Undefined behaviour in fs/read_write.c:251:11
signed integer overflow:
9223372036854775805 + 9223372036854775805 cannot be represented in
type 'long long int'
Use unsigned types to do math, it doesn't throw a UBSAN warning
when it does overflow.This patch doesn't change generated code.
Signed-off-by: Hongbo Yao <yaohongbo@huawei.com>
---
fs/read_write.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/read_write.c b/fs/read_write.c
index 8f08d4a2aa9a..0509e81afc8e 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -248,7 +248,7 @@ loff_t default_llseek(struct file *file, loff_t offset, int whence)
retval = file->f_pos;
goto out;
}
- offset += file->f_pos;
+ offset = (u64)file->f_pos + (u64)offset;
break;
case SEEK_DATA:
/*
--
2.20.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] fs: Avoid signed overflow UBSAN warning
2019-02-23 9:02 [PATCH] fs: Avoid signed overflow UBSAN warning Hongbo Yao
@ 2019-03-05 4:26 ` Matthew Wilcox
0 siblings, 0 replies; 2+ messages in thread
From: Matthew Wilcox @ 2019-03-05 4:26 UTC (permalink / raw)
To: Hongbo Yao; +Cc: viro, linux-fsdevel, linux-kernel, linuxarm
On Sat, Feb 23, 2019 at 05:02:10PM +0800, Hongbo Yao wrote:
> I ran into this:
> UBSAN: Undefined behaviour in fs/read_write.c:251:11
> signed integer overflow:
> 9223372036854775805 + 9223372036854775805 cannot be represented in
> type 'long long int'
>
> Use unsigned types to do math, it doesn't throw a UBSAN warning
> when it does overflow.This patch doesn't change generated code.
You don't need to be this verbose to fix it.
> - offset += file->f_pos;
> + offset = (u64)file->f_pos + (u64)offset;
offset += (u64)file->f_pos;
^ permalink raw reply [flat|nested] 2+ messages in thread
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2019-02-23 9:02 [PATCH] fs: Avoid signed overflow UBSAN warning Hongbo Yao
2019-03-05 4:26 ` Matthew Wilcox
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