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SubjectRe: [PATCH][next] ovl: fix null pointer dereference on null stack pointer on error return
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On 03/06/2020 17:11, Amir Goldstein wrote:
> On Wed, Jun 3, 2020 at 6:46 PM Colin King <colin.king@canonical.com> wrote:
>>
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> There are two error return paths where the call to path_put is
>> dereferencing the null pointer 'stack'. Fix this by avoiding the
>> error exit path via label 'out_err' that will lead to the path_put
>> calls and instead just return the error code directly.
>>
>> Addresses-Coverity: ("Dereference after null check)"
>> Fixes: 4155c10a0309 ("ovl: clean up getting lower layers")
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>
>
> Which branch is that based on?
> Doesn't seem to apply to master nor next

It was based on today's linux-next

>
>> ---
>> fs/overlayfs/super.c | 6 ++----
>> 1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
>> index 1094836f7e31..4be1b041b32c 100644
>> --- a/fs/overlayfs/super.c
>> +++ b/fs/overlayfs/super.c
>> @@ -1594,20 +1594,18 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
>> unsigned int i;
>> struct ovl_entry *oe;
>>
>> - err = -EINVAL;
>> if (!ofs->config.upperdir && numlower == 1) {
>> pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
>> - goto out_err;
>> + return ERR_PTR(-EINVAL);
>> } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
>> ofs->config.redirect_follow) {
>> pr_warn("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
>> ofs->config.nfs_export = false;
>> }
>>
>> - err = -ENOMEM;
>> stack = kcalloc(numlower, sizeof(struct path), GFP_KERNEL);
>> if (!stack)
>> - goto out_err;
>> + return ERR_PTR(-ENOMEM);
>>
>> err = -EINVAL;
>> for (i = 0; i < numlower; i++) {
>> --
>> 2.25.1
>>

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