Commit488dac0

Yicong Yang

authored and

torvalds

committed

libfs: fix error cast of negative value in simple_attr_write()

The attr->set() receive a value of u64, but simple_strtoll() is used fordoing the conversion. It will lead to the error cast if user inputs anegative value.Use kstrtoull() instead of simple_strtoll() to convert a string got fromthe user to an unsigned value. The former will return '-EINVAL' if itgets a negetive value, but the latter can't handle the situationcorrectly. Make 'val' unsigned long long as what kstrtoull() takes,this will eliminate the compile warning on no 64-bit architectures.Fixes:f7b8863 ("fs/libfs.c: fix simple_attr_write() on 32bit machines")Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>Signed-off-by: Andrew Morton <akpm@linux-foundation.org>Cc: Al Viro <viro@zeniv.linux.org.uk>Link:https://lkml.kernel.org/r/1605341356-11872-1-git-send-email-yangyicong@hisilicon.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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- libfs.c

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`‎fs/libfs.c‎`

Lines changed: 4 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -959,7 +959,7 @@ ssize_t simple_attr_write(struct file file, const char __user buf,`
`959`	`959`	`size_tlen,loff_t*ppos)`
`960`	`960`	`{`
`961`	`961`	`structsimple_attr*attr;`
`962`		`-u64val;`
	`962`	`+unsigned long longval;`
`963`	`963`	`size_tsize;`
`964`	`964`	`ssize_tret;`
`965`	`965`
`@@ -977,7 +977,9 @@ ssize_t simple_attr_write(struct file file, const char __user buf,`
`977`	`977`	`gotoout;`
`978`	`978`
`979`	`979`	`attr->set_buf[size]='\0';`
`980`		`-val=simple_strtoll(attr->set_buf,NULL,0);`
	`980`	`+ret=kstrtoull(attr->set_buf,0,&val);`
	`981`	`+if (ret)`
	`982`	`+gotoout;`
`981`	`983`	`ret=attr->set(attr->data,val);`
`982`	`984`	`if (ret==0)`
`983`	`985`	`ret=len;/* on success, claim we got the whole input */`

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Commit488dac0

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`‎fs/libfs.c‎`

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