ima: Check for ERR_PTR from dentry_path() in validate_hash_algo()

[Bradley Morgan]

From: Bradley Morgan <brads@xxxxxxxxxxxxxx>

commit 8861f6d5c0678a7c5089c7b272509fc5931b8437 upstream.

dentry_path() returns ERR_PTR(-ENAMETOOLONG) when the path exceeds the
buffer. validate_hash_algo() passes the result straight to
integrity_audit_msg() without checking. ERR_PTR is not NULL, so
integrity_audit_message() sees a valid pointer and calls strlen() on
it, which faults:

    BUG: unable to handle page fault for address: ffffffffffffffdc
    RIP: 0010:strlen+0x30/0xa0
    Call Trace:
     audit_log_untrustedstring+0x19/0x30
     integrity_audit_message+0x366/0x4f0
     ima_inode_setxattr+0x512/0x5f0

Check for IS_ERR() and use NULL instead, which makes the audit message
skip the name= field instead of crashing.

Fixes: 4f2946aa0c45 ("IMA: introduce a new policy option func=SETXATTR_CHECK")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: syzbot+5ebeb3089ea6439c37be@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/6a8f89e5.1d9ded08.62e62.00bf.GAE@xxxxxxxxxx/
Signed-off-by: Bradley Morgan <brads@xxxxxxxxxxxxxx>
Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
 security/integrity/ima/ima_appraise.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -754,6 +754,8 @@ static int validate_hash_algo(struct den
 		return -EACCES;
 
 	path = dentry_path(dentry, pathbuf, PATH_MAX);
+	if (IS_ERR(path))
+		path = NULL;
 
 	integrity_audit_msg(AUDIT_INTEGRITY_DATA, d_inode(dentry), path,
 			    "set_data", errmsg, -EACCES, 0);


>Thanks,
>
>Mathieu
>
>> 
>> 
>>> Fixes: 6357ec235c59 ("hazptrtorture: Fix hazptr ownership issue")
>>> Reported-by: kernel test robot <yi1.lai@xxxxxxxxx>
>>> Closes:
>https://lore.kernel.org/oe-lkp/202608130915.62b53936-lkp@xxxxxxxxx
>>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
>>> Reviewed-by: Bradley Morgan <brads@xxxxxxxxxxxxxx>
>>> Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
>>> Cc: Boqun Feng <boqun@xxxxxxxxxx>
>>> Cc: Bradley Morgan <brads@xxxxxxxxxxxxxx>
>>> Cc: <rcu@xxxxxxxxxxxxxxx>
>>> Cc: <lkmm@xxxxxxxxxxxxxxx>
>>> ---
>>> include/linux/hazptr.h | 4 +++-
>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>> 
>>> diff --git a/include/linux/hazptr.h b/include/linux/hazptr.h
>>> index 43122c5673bd..d1670121947a 100644
>>> --- a/include/linux/hazptr.h
>>> +++ b/include/linux/hazptr.h
>>> @@ -160,10 +160,12 @@ void hazptr_detach(struct hazptr_ctx *ctx)
>>> 	struct hazptr_slot *slot;
>>> 
>>> 	guard(preempt)();
>>> +	slot = ctx->slot;
>>> +	if (!slot->addr)
>>> +		return;
>>> #ifdef CONFIG_HAZPTR_DEBUG
>>> 	ctx->detach_task = ctx->detach_cpu = true;
>>> #endif
>>> -	slot = ctx->slot;
>>> 	if (unlikely(hazptr_slot_is_backup(ctx, slot)))
>>> 		return;
>>> 	hazptr_promote_to_backup_slot(ctx, slot);
>>> 
>> 
>> --- Thanks!
>>
>https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@xxxxxxxxx/
>
>
>

--- Thanks!
https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@xxxxxxxxx/