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Message-ID: <20190311060858.28654-4-gaoxiang25@huawei.com>
Date: Mon, 11 Mar 2019 14:08:57 +0800
From: Gao Xiang <gaoxiang25@...wei.com>
To: <stable@...r.kernel.org>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
LKML <linux-kernel@...r.kernel.org>,
<linux-erofs@...ts.ozlabs.org>, Chao Yu <yuchao0@...wei.com>,
Chao Yu <chao@...nel.org>, Miao Xie <miaoxie@...wei.com>,
Fang Wei <fangwei1@...wei.com>,
Gao Xiang <gaoxiang25@...wei.com>
Subject: [PATCH 4.19 4/5] staging: erofs: fix race of initializing xattrs of a inode at the same time
commit 62dc45979f3f8cb0ea67302a93bff686f0c46c5a upstream.
In real scenario, there could be several threads accessing xattrs
of the same xattr-uninitialized inode, and init_inode_xattrs()
almost at the same time.
That's actually an unexpected behavior, this patch closes the race.
Fixes: b17500a0fdba ("staging: erofs: introduce xattr & acl support")
Cc: <stable@...r.kernel.org> # 4.19+
Reviewed-by: Chao Yu <yuchao0@...wei.com>
Signed-off-by: Gao Xiang <gaoxiang25@...wei.com>
---
drivers/staging/erofs/internal.h | 11 ++++++++---
drivers/staging/erofs/xattr.c | 41 ++++++++++++++++++++++++++++------------
2 files changed, 37 insertions(+), 15 deletions(-)
diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h
index 1c048c412fb2..c70f0c5237ea 100644
--- a/drivers/staging/erofs/internal.h
+++ b/drivers/staging/erofs/internal.h
@@ -327,12 +327,17 @@ static inline erofs_off_t iloc(struct erofs_sb_info *sbi, erofs_nid_t nid)
return blknr_to_addr(sbi->meta_blkaddr) + (nid << sbi->islotbits);
}
-#define inode_set_inited_xattr(inode) (EROFS_V(inode)->flags |= 1)
-#define inode_has_inited_xattr(inode) (EROFS_V(inode)->flags & 1)
+/* atomic flag definitions */
+#define EROFS_V_EA_INITED_BIT 0
+
+/* bitlock definitions (arranged in reverse order) */
+#define EROFS_V_BL_XATTR_BIT (BITS_PER_LONG - 1)
struct erofs_vnode {
erofs_nid_t nid;
- unsigned int flags;
+
+ /* atomic flags (including bitlocks) */
+ unsigned long flags;
unsigned char data_mapping_mode;
/* inline size in bytes */
diff --git a/drivers/staging/erofs/xattr.c b/drivers/staging/erofs/xattr.c
index 890fa06bbcbb..955d024bf5a9 100644
--- a/drivers/staging/erofs/xattr.c
+++ b/drivers/staging/erofs/xattr.c
@@ -44,17 +44,24 @@ static inline void xattr_iter_end_final(struct xattr_iter *it)
static int init_inode_xattrs(struct inode *inode)
{
+ struct erofs_vnode *const vi = EROFS_V(inode);
struct xattr_iter it;
unsigned i;
struct erofs_xattr_ibody_header *ih;
struct erofs_sb_info *sbi;
- struct erofs_vnode *vi;
bool atomic_map;
+ int ret = 0;
- if (likely(inode_has_inited_xattr(inode)))
+ /* the most case is that xattrs of this inode are initialized. */
+ if (test_bit(EROFS_V_EA_INITED_BIT, &vi->flags))
return 0;
- vi = EROFS_V(inode);
+ if (wait_on_bit_lock(&vi->flags, EROFS_V_BL_XATTR_BIT, TASK_KILLABLE))
+ return -ERESTARTSYS;
+
+ /* someone has initialized xattrs for us? */
+ if (test_bit(EROFS_V_EA_INITED_BIT, &vi->flags))
+ goto out_unlock;
/*
* bypass all xattr operations if ->xattr_isize is not greater than
@@ -67,13 +74,16 @@ static int init_inode_xattrs(struct inode *inode)
if (vi->xattr_isize == sizeof(struct erofs_xattr_ibody_header)) {
errln("xattr_isize %d of nid %llu is not supported yet",
vi->xattr_isize, vi->nid);
- return -ENOTSUPP;
+ ret = -ENOTSUPP;
+ goto out_unlock;
} else if (vi->xattr_isize < sizeof(struct erofs_xattr_ibody_header)) {
if (unlikely(vi->xattr_isize)) {
DBG_BUGON(1);
- return -EIO; /* xattr ondisk layout error */
+ ret = -EIO;
+ goto out_unlock; /* xattr ondisk layout error */
}
- return -ENOATTR;
+ ret = -ENOATTR;
+ goto out_unlock;
}
sbi = EROFS_I_SB(inode);
@@ -81,8 +91,10 @@ static int init_inode_xattrs(struct inode *inode)
it.ofs = erofs_blkoff(iloc(sbi, vi->nid) + vi->inode_isize);
it.page = erofs_get_inline_page(inode, it.blkaddr);
- if (IS_ERR(it.page))
- return PTR_ERR(it.page);
+ if (IS_ERR(it.page)) {
+ ret = PTR_ERR(it.page);
+ goto out_unlock;
+ }
/* read in shared xattr array (non-atomic, see kmalloc below) */
it.kaddr = kmap(it.page);
@@ -95,7 +107,8 @@ static int init_inode_xattrs(struct inode *inode)
sizeof(uint), GFP_KERNEL);
if (vi->xattr_shared_xattrs == NULL) {
xattr_iter_end(&it, atomic_map);
- return -ENOMEM;
+ ret = -ENOMEM;
+ goto out_unlock;
}
/* let's skip ibody header */
@@ -112,7 +125,8 @@ static int init_inode_xattrs(struct inode *inode)
if (IS_ERR(it.page)) {
kfree(vi->xattr_shared_xattrs);
vi->xattr_shared_xattrs = NULL;
- return PTR_ERR(it.page);
+ ret = PTR_ERR(it.page);
+ goto out_unlock;
}
it.kaddr = kmap_atomic(it.page);
@@ -125,8 +139,11 @@ static int init_inode_xattrs(struct inode *inode)
}
xattr_iter_end(&it, atomic_map);
- inode_set_inited_xattr(inode);
- return 0;
+ set_bit(EROFS_V_EA_INITED_BIT, &vi->flags);
+
+out_unlock:
+ clear_and_wake_up_bit(EROFS_V_BL_XATTR_BIT, &vi->flags);
+ return ret;
}
struct xattr_iter_handlers {
--
2.14.5
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