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9p: retrieve fid from file when file instance exist.

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In the current setattr implementation in 9p, fid is always retrieved
from dentry no matter file instance exists or not. If so, there may be
some info related to opened file instance dropped. So it's better
to retrieve fid from file instance when it is passed to setattr.

for example:
fd=open("tmp", O_RDWR);
ftruncate(fd, 10);

The file context related with the fd will be lost as fid is always
retrieved from dentry, then the backend can't get the info of
file context. It is against the original intention of user and
may lead to bug.

Link: http://lkml.kernel.org/r/20200710101548.10108-1-jianyong.wu@arm.com
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
This commit is contained in:
Jianyong Wu
2020-07-10 18:15:48 +08:00
committed by Dominique Martinet
parent 74d6a5d566
commit 6624664160
2 changed files with 14 additions and 4 deletions
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9
fs/9p/vfs_inode.c
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@@ -1090,7 +1090,7 @@ static int v9fs_vfs_setattr(struct dentry *dentry, struct iattr *iattr)
{
int retval;
struct v9fs_session_info *v9ses;
struct p9_fid *fid;
struct p9_fid *fid = NULL;
struct p9_wstat wstat;
p9_debug(P9_DEBUG_VFS, "\n");
@@ -1100,7 +1100,12 @@ static int v9fs_vfs_setattr(struct dentry *dentry, struct iattr *iattr)
retval = -EPERM;
v9ses = v9fs_dentry2v9ses(dentry);
fid = v9fs_fid_lookup(dentry);
if (iattr->ia_valid & ATTR_FILE) {
fid = iattr->ia_file->private_data;
WARN_ON(!fid);
}
if (!fid)
fid = v9fs_fid_lookup(dentry);
if(IS_ERR(fid))
return PTR_ERR(fid);