[PATCH 5.15 268/317] NFSv4.2: fix nfs4_listxattr kernel BUG at mm/usercopy.c:102

Sasha Levin
2024-03-24T23:39:21Z

From: Jorge Mora <jmora1300@gmail.com>

[ Upstream commit 251a658bbfceafb4d58c76b77682c8bf7bcfad65 ]

A call to listxattr() with a buffer size = 0 returns the actual
size of the buffer needed for a subsequent call. When size > 0,
nfs4_listxattr() does not return an error because either
generic_listxattr() or nfs4_listxattr_nfs4_label() consumes
exactly all the bytes then size is 0 when calling
nfs4_listxattr_nfs4_user() which then triggers the following
kernel BUG:

[ 99.403778] kernel BUG at mm/usercopy.c:102!
[ 99.404063] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
[ 99.408463] CPU: 0 PID: 3310 Comm: python3 Not tainted 6.6.0-61.fc40.aarch64 #1
[ 99.415827] Call trace:
[ 99.415985] usercopy_abort+0x70/0xa0
[ 99.416227] __check_heap_object+0x134/0x158
[ 99.416505] check_heap_object+0x150/0x188
[ 99.416696] __check_object_size.part.0+0x78/0x168
[ 99.416886] __check_object_size+0x28/0x40
[ 99.417078] listxattr+0x8c/0x120
[ 99.417252] path_listxattr+0x78/0xe0
[ 99.417476] __arm64_sys_listxattr+0x28/0x40
[ 99.417723] invoke_syscall+0x78/0x100
[ 99.417929] el0_svc_common.constprop.0+0x48/0xf0
[ 99.418186] do_el0_svc+0x24/0x38
[ 99.418376] el0_svc+0x3c/0x110
[ 99.418554] el0t_64_sync_handler+0x120/0x130
[ 99.418788] el0t_64_sync+0x194/0x198
[ 99.418994] Code: aa0003e3 d000a3e0 91310000 97f49bdb (d4210000)

Issue is reproduced when generic_listxattr() returns 'system.nfs4_acl',
thus calling lisxattr() with size = 16 will trigger the bug.

Add check on nfs4_listxattr() to return ERANGE error when it is
called with size > 0 and the return value is greater than size.

Fixes: 012a211abd5d ("NFSv4.2: hook in the user extended attribute handlers")
Signed-off-by: Jorge Mora <mora@netapp.com>
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfs/nfs4proc.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index a865b384f0fc0..925ad7dbe6a0d 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -10517,29 +10517,33 @@ const struct nfs4_minor_version_ops *nfs_v4_minor_ops[] = {
static ssize_t nfs4_listxattr(struct dentry *dentry, char *list, size_t size)
{
ssize_t error, error2, error3;
+ size_t left = size;

- error = generic_listxattr(dentry, list, size);
+ error = generic_listxattr(dentry, list, left);
if (error < 0)
return error;
if (list) {
list += error;
- size -= error;
+ left -= error;
}

- error2 = nfs4_listxattr_nfs4_label(d_inode(dentry), list, size);
+ error2 = nfs4_listxattr_nfs4_label(d_inode(dentry), list, left);
if (error2 < 0)
return error2;

if (list) {
list += error2;
- size -= error2;
+ left -= error2;
}

- error3 = nfs4_listxattr_nfs4_user(d_inode(dentry), list, size);
+ error3 = nfs4_listxattr_nfs4_user(d_inode(dentry), list, left);
if (error3 < 0)
return error3;

- return error + error2 + error3;
+ error += error2 + error3;
+ if (size && error > size)
+ return -ERANGE;
+ return error;
}

static void nfs4_enable_swap(struct inode *inode)
--
2.43.0