[v2] udf: avoid uninitialized variable use

Message ID 5491623.oZlI0zcRmi@wuerfel
State New
Headers show

Commit Message

Arnd Bergmann Jan. 1, 2016, 2:21 p.m.
A new warning about a real bug has come up from a recent cleanup:

fs/udf/inode.c: In function 'udf_setup_indirect_aext':
fs/udf/inode.c:1927:28: warning: 'adsize' may be used uninitialized in this function [-Wmaybe-uninitialized]

If the alloc_type is neither ICBTAG_FLAG_AD_SHORT nor ICBTAG_FLAG_AD_LONG,
the value of adsize is undefined. This changes the code to use zero for adsize
in that case, which may be the correct solution, though I have not looked
at the code in enough detail to know if it should be something else instead.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Fixes: fcea62babc81 ("udf: Factor out code for creating indirect extent")
---
sorry for missing another instance the first time around. The warning is
a bit unreliable and it seems in my first configuration I got it only
for one of the two instances that show it in other configuration.

After checking the remaining functions in this file for the same possible
problem, I found that the other functions use either 'BUG()' or 'return -EIO'
in the 'else' path, so I assume the two functions here should one of those
as well, but I don't know which.


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Comments

Jan Kara Jan. 4, 2016, 9:56 a.m. | #1
On Fri 01-01-16 15:21:54, Arnd Bergmann wrote:
> A new warning about a real bug has come up from a recent cleanup:

> 

> fs/udf/inode.c: In function 'udf_setup_indirect_aext':

> fs/udf/inode.c:1927:28: warning: 'adsize' may be used uninitialized in this function [-Wmaybe-uninitialized]

> 

> If the alloc_type is neither ICBTAG_FLAG_AD_SHORT nor ICBTAG_FLAG_AD_LONG,

> the value of adsize is undefined. This changes the code to use zero for adsize

> in that case, which may be the correct solution, though I have not looked

> at the code in enough detail to know if it should be something else instead.

> 

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

> Fixes: fcea62babc81 ("udf: Factor out code for creating indirect extent")

> ---

> sorry for missing another instance the first time around. The warning is

> a bit unreliable and it seems in my first configuration I got it only

> for one of the two instances that show it in other configuration.

> 

> After checking the remaining functions in this file for the same possible

> problem, I found that the other functions use either 'BUG()' or 'return -EIO'

> in the 'else' path, so I assume the two functions here should one of those

> as well, but I don't know which.


Callers of these functions make sure alloc_type is one of the two valid
ones. However for future-proofing you're right that probably we should
handle the invalid case as well. Setting adsize to zero is problematic -
not sure what the code would actually do but it wouldn't definitely work.
I'd just return -EIO. Attached is the patch I have merged.

								Honza
> 

> diff --git a/fs/udf/inode.c b/fs/udf/inode.c

> index 5b83351041a4..42f68dd7e6ef 100644

> --- a/fs/udf/inode.c

> +++ b/fs/udf/inode.c

> @@ -1890,6 +1890,8 @@ int udf_setup_indirect_aext(struct inode *inode, int block,

>  		adsize = sizeof(struct short_ad);

>  	else if (UDF_I(inode)->i_alloc_type == ICBTAG_FLAG_AD_LONG)

>  		adsize = sizeof(struct long_ad);

> +	else

> +		adsize = 0;

>  

>  	neloc.logicalBlockNum = block;

>  	neloc.partitionReferenceNum = epos->block.partitionReferenceNum;

> @@ -1963,6 +1965,8 @@ int __udf_add_aext(struct inode *inode, struct extent_position *epos,

>  		adsize = sizeof(struct short_ad);

>  	else if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_LONG)

>  		adsize = sizeof(struct long_ad);

> +	else

> +		adsize = 0;

>  

>  	if (!epos->bh) {

>  		WARN_ON(iinfo->i_lenAlloc !=

> 

-- 
Jan Kara <jack@suse.com>
SUSE Labs, CRFrom 4f1b1519f7bec44ded3c2c4d46a2594c01446dc8 Mon Sep 17 00:00:00 2001
From: Arnd Bergmann <arnd@arndb.de>

Date: Fri, 1 Jan 2016 15:21:54 +0100
Subject: [PATCH] udf: avoid uninitialized variable use

A new warning has come up from a recent cleanup:

fs/udf/inode.c: In function 'udf_setup_indirect_aext':
fs/udf/inode.c:1927:28: warning: 'adsize' may be used uninitialized in this function [-Wmaybe-uninitialized]

If the alloc_type is neither ICBTAG_FLAG_AD_SHORT nor
ICBTAG_FLAG_AD_LONG, the value of adsize is undefined. Currently,
callers of these functions make sure alloc_type is one of the two valid
ones but for future proofing make sure we handle the case of invalid
alloc type as well.  This changes the code to return -EIOin that case.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Fixes: fcea62babc81 ("udf: Factor out code for creating indirect extent")
Signed-off-by: Jan Kara <jack@suse.cz>

---
 fs/udf/inode.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 846294891925..91d8fa9d87a4 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1889,6 +1889,8 @@ int udf_setup_indirect_aext(struct inode *inode, int block,
 		adsize = sizeof(struct short_ad);
 	else if (UDF_I(inode)->i_alloc_type == ICBTAG_FLAG_AD_LONG)
 		adsize = sizeof(struct long_ad);
+	else
+		return -EIO;
 
 	neloc.logicalBlockNum = block;
 	neloc.partitionReferenceNum = epos->block.partitionReferenceNum;
@@ -1962,6 +1964,8 @@ int __udf_add_aext(struct inode *inode, struct extent_position *epos,
 		adsize = sizeof(struct short_ad);
 	else if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_LONG)
 		adsize = sizeof(struct long_ad);
+	else
+		return -EIO;
 
 	if (!epos->bh) {
 		WARN_ON(iinfo->i_lenAlloc !=
-- 
2.6.2


Arnd Bergmann Jan. 4, 2016, 10:46 a.m. | #2
On Monday 04 January 2016 10:56:05 Jan Kara wrote:
> On Fri 01-01-16 15:21:54, Arnd Bergmann wrote:

> > A new warning about a real bug has come up from a recent cleanup:

> > 

> > fs/udf/inode.c: In function 'udf_setup_indirect_aext':

> > fs/udf/inode.c:1927:28: warning: 'adsize' may be used uninitialized in this function [-Wmaybe-uninitialized]

> > 

> > If the alloc_type is neither ICBTAG_FLAG_AD_SHORT nor ICBTAG_FLAG_AD_LONG,

> > the value of adsize is undefined. This changes the code to use zero for adsize

> > in that case, which may be the correct solution, though I have not looked

> > at the code in enough detail to know if it should be something else instead.

> > 

> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>

> > Fixes: fcea62babc81 ("udf: Factor out code for creating indirect extent")

> > ---

> > sorry for missing another instance the first time around. The warning is

> > a bit unreliable and it seems in my first configuration I got it only

> > for one of the two instances that show it in other configuration.

> > 

> > After checking the remaining functions in this file for the same possible

> > problem, I found that the other functions use either 'BUG()' or 'return -EIO'

> > in the 'else' path, so I assume the two functions here should one of those

> > as well, but I don't know which.

> 

> Callers of these functions make sure alloc_type is one of the two valid

> ones. However for future-proofing you're right that probably we should

> handle the invalid case as well. Setting adsize to zero is problematic -

> not sure what the code would actually do but it wouldn't definitely work.

> I'd just return -EIO. Attached is the patch I have merged.

> 

> 


Looks good, thanks!

	Arnd
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Patch

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 5b83351041a4..42f68dd7e6ef 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1890,6 +1890,8 @@  int udf_setup_indirect_aext(struct inode *inode, int block,
 		adsize = sizeof(struct short_ad);
 	else if (UDF_I(inode)->i_alloc_type == ICBTAG_FLAG_AD_LONG)
 		adsize = sizeof(struct long_ad);
+	else
+		adsize = 0;
 
 	neloc.logicalBlockNum = block;
 	neloc.partitionReferenceNum = epos->block.partitionReferenceNum;
@@ -1963,6 +1965,8 @@  int __udf_add_aext(struct inode *inode, struct extent_position *epos,
 		adsize = sizeof(struct short_ad);
 	else if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_LONG)
 		adsize = sizeof(struct long_ad);
+	else
+		adsize = 0;
 
 	if (!epos->bh) {
 		WARN_ON(iinfo->i_lenAlloc !=