linux-kernel - [PATCH 2/2] afs: Fix incorrect freeing of the ACL passed to the YFS ACL store op

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Date:   Tue, 03 Nov 2020 16:33:07 +0000
From:   David Howells <dhowells@...hat.com>
To:     torvalds@...ux-foundation.org
Cc:     dhowells@...hat.com, linux-afs@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] afs: Fix incorrect freeing of the ACL passed to the YFS
 ACL store op

The cleanup for the yfs_store_opaque_acl2_operation calls the wrong
function to destroy the ACL content buffer.  It's an afs_acl struct, not a
yfs_acl struct - and the free function for latter may pass invalid pointers
to kfree().

Fix this by using the afs_acl_put() function.  The yfs_acl_put() function
is then no longer used and can be removed.

	general protection fault, probably for non-canonical address 0x7ebde00000000: 0000 [#1] SMP PTI
	...
	RIP: 0010:compound_head+0x0/0x11
	...
	Call Trace:
	 virt_to_cache+0x8/0x51
	 ? yfs_free_opaque_acl+0x16/0x29
	 kfree+0x5d/0x79
	 yfs_free_opaque_acl+0x16/0x29
	 afs_put_operation+0x60/0x114
	 __vfs_setxattr+0x67/0x72
	 __vfs_setxattr_noperm+0x66/0xe9
	 vfs_setxattr+0x67/0xce
	 setxattr+0x14e/0x184
	 ? __handle_mm_fault+0x4c8/0x4f8
	 ? handle_mm_fault+0x123/0x1ef
	 __do_sys_fsetxattr+0x66/0x8f
	 do_syscall_64+0x2d/0x3a
	 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept")
Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/afs/xattr.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/fs/afs/xattr.c b/fs/afs/xattr.c
index 38884d6c57cd..95c573dcda11 100644
--- a/fs/afs/xattr.c
+++ b/fs/afs/xattr.c
@@ -148,11 +148,6 @@ static const struct xattr_handler afs_xattr_afs_acl_handler = {
 	.set    = afs_xattr_set_acl,
 };
 
-static void yfs_acl_put(struct afs_operation *op)
-{
-	yfs_free_opaque_acl(op->yacl);
-}
-
 static const struct afs_operation_ops yfs_fetch_opaque_acl_operation = {
 	.issue_yfs_rpc	= yfs_fs_fetch_opaque_acl,
 	.success	= afs_acl_success,
@@ -246,7 +241,7 @@ static int afs_xattr_get_yfs(const struct xattr_handler *handler,
 static const struct afs_operation_ops yfs_store_opaque_acl2_operation = {
 	.issue_yfs_rpc	= yfs_fs_store_opaque_acl2,
 	.success	= afs_acl_success,
-	.put		= yfs_acl_put,
+	.put		= afs_acl_put,
 };
 
 /*