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authorFilipe Manana <fdmanana@suse.com>2021-02-26 17:51:44 +0000
committerDavid Sterba <dsterba@suse.com>2021-03-02 17:47:56 +0100
commitfd57a98d6f0c98fa295813087f13afb26c224e73 (patch)
tree41b47ad2b1f9bafdd6ab25c6b86ff0ac73786271 /fs/btrfs/xattr.c
parent4d14c5cde5c268a2bc26addecf09489cb953ef64 (diff)
btrfs: fix warning when creating a directory with smack enabled
When we have smack enabled, during the creation of a directory smack may attempt to add a "smack transmute" xattr on the inode, which results in the following warning and trace: WARNING: CPU: 3 PID: 2548 at fs/btrfs/transaction.c:537 start_transaction+0x489/0x4f0 Modules linked in: nft_objref nf_conntrack_netbios_ns (...) CPU: 3 PID: 2548 Comm: mkdir Not tainted 5.9.0-rc2smack+ #81 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 RIP: 0010:start_transaction+0x489/0x4f0 Code: e9 be fc ff ff (...) RSP: 0018:ffffc90001887d10 EFLAGS: 00010202 RAX: ffff88816f1e0000 RBX: 0000000000000201 RCX: 0000000000000003 RDX: 0000000000000201 RSI: 0000000000000002 RDI: ffff888177849000 RBP: ffff888177849000 R08: 0000000000000001 R09: 0000000000000004 R10: ffffffff825e8f7a R11: 0000000000000003 R12: ffffffffffffffe2 R13: 0000000000000000 R14: ffff88803d884270 R15: ffff8881680d8000 FS: 00007f67317b8440(0000) GS:ffff88817bcc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f67247a22a8 CR3: 000000004bfbc002 CR4: 0000000000370ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: ? slab_free_freelist_hook+0xea/0x1b0 ? trace_hardirqs_on+0x1c/0xe0 btrfs_setxattr_trans+0x3c/0xf0 __vfs_setxattr+0x63/0x80 smack_d_instantiate+0x2d3/0x360 security_d_instantiate+0x29/0x40 d_instantiate_new+0x38/0x90 btrfs_mkdir+0x1cf/0x1e0 vfs_mkdir+0x14f/0x200 do_mkdirat+0x6d/0x110 do_syscall_64+0x2d/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f673196ae6b Code: 8b 05 11 (...) RSP: 002b:00007ffc3c679b18 EFLAGS: 00000246 ORIG_RAX: 0000000000000053 RAX: ffffffffffffffda RBX: 00000000000001ff RCX: 00007f673196ae6b RDX: 0000000000000000 RSI: 00000000000001ff RDI: 00007ffc3c67a30d RBP: 00007ffc3c67a30d R08: 00000000000001ff R09: 0000000000000000 R10: 000055d3e39fe930 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffc3c679cd8 R14: 00007ffc3c67a30d R15: 00007ffc3c679ce0 irq event stamp: 11029 hardirqs last enabled at (11037): [<ffffffff81153fe6>] console_unlock+0x486/0x670 hardirqs last disabled at (11044): [<ffffffff81153c01>] console_unlock+0xa1/0x670 softirqs last enabled at (8864): [<ffffffff81e0102f>] asm_call_on_stack+0xf/0x20 softirqs last disabled at (8851): [<ffffffff81e0102f>] asm_call_on_stack+0xf/0x20 This happens because at btrfs_mkdir() we call d_instantiate_new() while holding a transaction handle, which results in the following call chain: btrfs_mkdir() trans = btrfs_start_transaction(root, 5); d_instantiate_new() smack_d_instantiate() __vfs_setxattr() btrfs_setxattr_trans() btrfs_start_transaction() start_transaction() WARN_ON() --> a tansaction start has TRANS_EXTWRITERS set in its type h->orig_rsv = h->block_rsv h->block_rsv = NULL btrfs_end_transaction(trans) Besides the warning triggered at start_transaction, we set the handle's block_rsv to NULL which may cause some surprises later on. So fix this by making btrfs_setxattr_trans() not start a transaction when we already have a handle on one, stored in current->journal_info, and use that handle. We are good to use the handle because at btrfs_mkdir() we did reserve space for the xattr and the inode item. Reported-by: Casey Schaufler <casey@schaufler-ca.com> CC: stable@vger.kernel.org # 5.4+ Acked-by: Casey Schaufler <casey@schaufler-ca.com> Tested-by: Casey Schaufler <casey@schaufler-ca.com> Link: https://lore.kernel.org/linux-btrfs/434d856f-bd7b-4889-a6ec-e81aaebfa735@schaufler-ca.com/ Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/xattr.c')
-rw-r--r--fs/btrfs/xattr.c31
1 files changed, 27 insertions, 4 deletions
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index af6246f36a9e..03135dbb318a 100644
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -229,11 +229,33 @@ int btrfs_setxattr_trans(struct inode *inode, const char *name,
{
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_trans_handle *trans;
+ const bool start_trans = (current->journal_info == NULL);
int ret;
- trans = btrfs_start_transaction(root, 2);
- if (IS_ERR(trans))
- return PTR_ERR(trans);
+ if (start_trans) {
+ /*
+ * 1 unit for inserting/updating/deleting the xattr
+ * 1 unit for the inode item update
+ */
+ trans = btrfs_start_transaction(root, 2);
+ if (IS_ERR(trans))
+ return PTR_ERR(trans);
+ } else {
+ /*
+ * This can happen when smack is enabled and a directory is being
+ * created. It happens through d_instantiate_new(), which calls
+ * smack_d_instantiate(), which in turn calls __vfs_setxattr() to
+ * set the transmute xattr (XATTR_NAME_SMACKTRANSMUTE) on the
+ * inode. We have already reserved space for the xattr and inode
+ * update at btrfs_mkdir(), so just use the transaction handle.
+ * We don't join or start a transaction, as that will reset the
+ * block_rsv of the handle and trigger a warning for the start
+ * case.
+ */
+ ASSERT(strncmp(name, XATTR_SECURITY_PREFIX,
+ XATTR_SECURITY_PREFIX_LEN) == 0);
+ trans = current->journal_info;
+ }
ret = btrfs_setxattr(trans, inode, name, value, size, flags);
if (ret)
@@ -244,7 +266,8 @@ int btrfs_setxattr_trans(struct inode *inode, const char *name,
ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
BUG_ON(ret);
out:
- btrfs_end_transaction(trans);
+ if (start_trans)
+ btrfs_end_transaction(trans);
return ret;
}