6.12-stable review patch. If anyone has any objections, please let me know.
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From: Christian Schoenebeck linux_oss@crudebyte.com
[ Upstream commit 3f61ac7c65bdb26accb52f9db66313597e759821 ]
When a 9p tree was mounted with option 'posixacl', parent directory had a default ACL set for its subdirectories, e.g.:
setfacl -m default:group:simpsons:rwx parentdir
then creating a subdirectory crashed 9p client, as v9fs_fid_add() call in function v9fs_vfs_mkdir_dotl() sets the passed 'fid' pointer to NULL (since dafbe689736) even though the subsequent v9fs_set_create_acl() call expects a valid non-NULL 'fid' pointer:
[ 37.273191] BUG: kernel NULL pointer dereference, address: 0000000000000000 ... [ 37.322338] Call Trace: [ 37.323043] <TASK> [ 37.323621] ? __die (arch/x86/kernel/dumpstack.c:421 arch/x86/kernel/dumpstack.c:434) [ 37.324448] ? page_fault_oops (arch/x86/mm/fault.c:714) [ 37.325532] ? search_module_extables (kernel/module/main.c:3733) [ 37.326742] ? p9_client_walk (net/9p/client.c:1165) 9pnet [ 37.328006] ? search_bpf_extables (kernel/bpf/core.c:804) [ 37.329142] ? exc_page_fault (./arch/x86/include/asm/paravirt.h:686 arch/x86/mm/fault.c:1488 arch/x86/mm/fault.c:1538) [ 37.330196] ? asm_exc_page_fault (./arch/x86/include/asm/idtentry.h:574) [ 37.331330] ? p9_client_walk (net/9p/client.c:1165) 9pnet [ 37.332562] ? v9fs_fid_xattr_get (fs/9p/xattr.c:30) 9p [ 37.333824] v9fs_fid_xattr_set (fs/9p/fid.h:23 fs/9p/xattr.c:121) 9p [ 37.335077] v9fs_set_acl (fs/9p/acl.c:276) 9p [ 37.336112] v9fs_set_create_acl (fs/9p/acl.c:307) 9p [ 37.337326] v9fs_vfs_mkdir_dotl (fs/9p/vfs_inode_dotl.c:411) 9p [ 37.338590] vfs_mkdir (fs/namei.c:4313) [ 37.339535] do_mkdirat (fs/namei.c:4336) [ 37.340465] __x64_sys_mkdir (fs/namei.c:4354) [ 37.341455] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) [ 37.342447] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
Fix this by simply swapping the sequence of these two calls in v9fs_vfs_mkdir_dotl(), i.e. calling v9fs_set_create_acl() before v9fs_fid_add().
Fixes: dafbe689736f ("9p fid refcount: cleanup p9_fid_put calls") Reported-by: syzbot+5b667f9a1fee4ba3775a@syzkaller.appspotmail.com Signed-off-by: Christian Schoenebeck linux_oss@crudebyte.com Message-ID: E1tsiI6-002iMG-Kh@kylie.crudebyte.com Signed-off-by: Dominique Martinet asmadeus@codewreck.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/9p/vfs_inode_dotl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c index 143ac03b7425c..3397939fd2d5a 100644 --- a/fs/9p/vfs_inode_dotl.c +++ b/fs/9p/vfs_inode_dotl.c @@ -407,8 +407,8 @@ static int v9fs_vfs_mkdir_dotl(struct mnt_idmap *idmap, err); goto error; } - v9fs_fid_add(dentry, &fid); v9fs_set_create_acl(inode, fid, dacl, pacl); + v9fs_fid_add(dentry, &fid); d_instantiate(dentry, inode); err = 0; inc_nlink(dir);