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author | Al Viro <viro@zeniv.linux.org.uk> | 2021-03-05 17:36:04 -0500 |
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committer | Steve French <stfrench@microsoft.com> | 2021-04-25 16:28:23 -0500 |
commit | f6a9bc336b600e1266e6eebb0972d75d5b93aea9 (patch) | |
tree | 62432d7b429006e2cdab9e9750565eec9e868fd9 /fs/cifs/dir.c | |
parent | 8e33cf20ceb7f6d7a7e039f9f82a0cd1f3a6f964 (diff) | |
download | linux-f6a9bc336b600e1266e6eebb0972d75d5b93aea9.tar.bz2 |
cifs: allocate buffer in the caller of build_path_from_dentry()
build_path_from_dentry() open-codes dentry_path_raw(). The reason
we can't use dentry_path_raw() in there (and postprocess the
result as needed) is that the callers of build_path_from_dentry()
expect that the object to be freed on cleanup and the string to
be used are at the same address. That's painful, since the path
is naturally built end-to-beginning - we start at the leaf and
go through the ancestors, accumulating the pathname.
Life would be easier if we left the buffer allocation to callers.
It wouldn't be exact-sized buffer, but none of the callers keep
the result for long - it's always freed before the caller returns.
So there's no need to do exact-sized allocation; better use
__getname()/__putname(), same as we do for pathname arguments
of syscalls. What's more, there's no need to do allocation under
spinlocks, so GFP_ATOMIC is not needed.
Next patch will replace the open-coded dentry_path_raw() (in
build_path_from_dentry_optional_prefix()) with calling the real
thing. This patch only introduces wrappers for allocating/freeing
the buffers and switches to new calling conventions:
build_path_from_dentry(dentry, buf)
expects buf to be address of a page-sized object or NULL,
return value is a pathname built inside that buffer on success,
ERR_PTR(-ENOMEM) if buf is NULL and ERR_PTR(-ENAMETOOLONG) if
the pathname won't fit into page. Note that we don't need to
check for failure when allocating the buffer in the caller -
build_path_from_dentry() will do the right thing.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs/cifs/dir.c')
-rw-r--r-- | fs/cifs/dir.c | 69 |
1 files changed, 34 insertions, 35 deletions
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c index 01e26f811885..6e855f004f50 100644 --- a/fs/cifs/dir.c +++ b/fs/cifs/dir.c @@ -79,29 +79,33 @@ cifs_build_path_to_root(struct smb3_fs_context *ctx, struct cifs_sb_info *cifs_s /* Note: caller must free return buffer */ const char * -build_path_from_dentry(struct dentry *direntry) +build_path_from_dentry(struct dentry *direntry, void *page) { struct cifs_sb_info *cifs_sb = CIFS_SB(direntry->d_sb); struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb); bool prefix = tcon->Flags & SMB_SHARE_IS_IN_DFS; - return build_path_from_dentry_optional_prefix(direntry, + return build_path_from_dentry_optional_prefix(direntry, page, prefix); } char * -build_path_from_dentry_optional_prefix(struct dentry *direntry, bool prefix) +build_path_from_dentry_optional_prefix(struct dentry *direntry, void *page, + bool prefix) { struct dentry *temp; int namelen; int dfsplen; int pplen = 0; - char *full_path; + char *full_path = page; char dirsep; struct cifs_sb_info *cifs_sb = CIFS_SB(direntry->d_sb); struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb); unsigned seq; + if (unlikely(!page)) + return ERR_PTR(-ENOMEM); + dirsep = CIFS_DIR_SEP(cifs_sb); if (prefix) dfsplen = strnlen(tcon->treeName, MAX_TREE_SIZE + 1); @@ -118,17 +122,12 @@ cifs_bp_rename_retry: for (temp = direntry; !IS_ROOT(temp);) { namelen += (1 + temp->d_name.len); temp = temp->d_parent; - if (temp == NULL) { - cifs_dbg(VFS, "corrupt dentry\n"); - rcu_read_unlock(); - return NULL; - } } rcu_read_unlock(); - full_path = kmalloc(namelen+1, GFP_ATOMIC); - if (full_path == NULL) - return full_path; + if (namelen >= PAGE_SIZE) + return ERR_PTR(-ENAMETOOLONG); + full_path[namelen] = 0; /* trailing null */ rcu_read_lock(); for (temp = direntry; !IS_ROOT(temp);) { @@ -145,12 +144,6 @@ cifs_bp_rename_retry: } spin_unlock(&temp->d_lock); temp = temp->d_parent; - if (temp == NULL) { - cifs_dbg(VFS, "corrupt dentry\n"); - rcu_read_unlock(); - kfree(full_path); - return NULL; - } } rcu_read_unlock(); if (namelen != dfsplen + pplen || read_seqretry(&rename_lock, seq)) { @@ -159,7 +152,6 @@ cifs_bp_rename_retry: /* presumably this is only possible if racing with a rename of one of the parent directories (we can not lock the dentries above us to prevent this, but retrying should be harmless) */ - kfree(full_path); goto cifs_bp_rename_retry; } /* DIR_SEP already set for byte 0 / vs \ but not for @@ -233,7 +225,8 @@ cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned int xid, int desired_access; struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb); struct cifs_tcon *tcon = tlink_tcon(tlink); - const char *full_path = NULL; + const char *full_path; + void *page = alloc_dentry_path(); FILE_ALL_INFO *buf = NULL; struct inode *newinode = NULL; int disposition; @@ -244,9 +237,11 @@ cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned int xid, if (tcon->ses->server->oplocks) *oplock = REQ_OPLOCK; - full_path = build_path_from_dentry(direntry); - if (!full_path) - return -ENOMEM; + full_path = build_path_from_dentry(direntry, page); + if (IS_ERR(full_path)) { + free_dentry_path(page); + return PTR_ERR(full_path); + } if (tcon->unix_ext && cap_unix(tcon->ses) && !tcon->broken_posix_open && (CIFS_UNIX_POSIX_PATH_OPS_CAP & @@ -448,7 +443,7 @@ cifs_create_set_dentry: out: kfree(buf); - kfree(full_path); + free_dentry_path(page); return rc; out_err: @@ -619,7 +614,8 @@ int cifs_mknod(struct user_namespace *mnt_userns, struct inode *inode, struct cifs_sb_info *cifs_sb; struct tcon_link *tlink; struct cifs_tcon *tcon; - const char *full_path = NULL; + const char *full_path; + void *page; if (!old_valid_dev(device_number)) return -EINVAL; @@ -629,13 +625,13 @@ int cifs_mknod(struct user_namespace *mnt_userns, struct inode *inode, if (IS_ERR(tlink)) return PTR_ERR(tlink); + page = alloc_dentry_path(); tcon = tlink_tcon(tlink); - xid = get_xid(); - full_path = build_path_from_dentry(direntry); - if (full_path == NULL) { - rc = -ENOMEM; + full_path = build_path_from_dentry(direntry, page); + if (IS_ERR(full_path)) { + rc = PTR_ERR(full_path); goto mknod_out; } @@ -644,7 +640,7 @@ int cifs_mknod(struct user_namespace *mnt_userns, struct inode *inode, device_number); mknod_out: - kfree(full_path); + free_dentry_path(page); free_xid(xid); cifs_put_tlink(tlink); return rc; @@ -660,7 +656,8 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry, struct tcon_link *tlink; struct cifs_tcon *pTcon; struct inode *newInode = NULL; - const char *full_path = NULL; + const char *full_path; + void *page; xid = get_xid(); @@ -687,11 +684,13 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry, /* can not grab the rename sem here since it would deadlock in the cases (beginning of sys_rename itself) in which we already have the sb rename sem */ - full_path = build_path_from_dentry(direntry); - if (full_path == NULL) { + page = alloc_dentry_path(); + full_path = build_path_from_dentry(direntry, page); + if (IS_ERR(full_path)) { cifs_put_tlink(tlink); free_xid(xid); - return ERR_PTR(-ENOMEM); + free_dentry_path(page); + return ERR_CAST(full_path); } if (d_really_is_positive(direntry)) { @@ -727,7 +726,7 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry, } newInode = ERR_PTR(rc); } - kfree(full_path); + free_dentry_path(page); cifs_put_tlink(tlink); free_xid(xid); return d_splice_alias(newInode, direntry); |