stat(): Add logic to avoid infinite recursive in circular paths containing soft links.
This commit is contained in:
Gregory Nutt
parent
62a1f6f110
commit
b758176963
145
fs/vfs/fs_stat.c
145
fs/vfs/fs_stat.c
@ -47,6 +47,25 @@
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#include "inode/inode.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#ifdef CONFIG_PSEUDOFS_SOFTLINKS
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/* Reset, preserving the number of symbolic links encountered so far */
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# define RESET_BUF(b) \
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{ \
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uint16_t save = (b)->st_count; \
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memset((b), 0, sizeof(struct stat)); \
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(b)->st_count = save; \
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}
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#else
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/* Reset everything */
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# define RESET_BUF(b) memset((b), 0, sizeof(struct stat));
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#endif
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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@ -59,7 +78,7 @@ static inline int statpseudo(FAR struct inode *inode, FAR struct stat *buf)
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{
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/* Most of the stat entries just do not apply */
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memset(buf, 0, sizeof(struct stat));
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RESET_BUF(buf);
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if (INODE_IS_SPECIAL(inode))
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{
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@ -95,26 +114,36 @@ static inline int statpseudo(FAR struct inode *inode, FAR struct stat *buf)
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{
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int ret;
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/* stat() the target of the soft link.
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/* Increment the link counter. This is necesssary to avoid
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* infinite recursion if loops are encountered in the traversal.
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* If we encounter more SYMLOOP_MAX symbolic links at any time
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* during the travrsal, error out.
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*
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* Note: We don't really handle links to links nicely. I suppose
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* that we should repetitively deference the symbolic link inodes
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* until we discover the true target link?
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* NOTE: That inode_search() will automatically skip over
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* consecutive, intermediate symbolic links. Those numbers will
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* not be included in the total.
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*/
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ret = stat((FAR const char *)inode->u.i_link, buf);
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if (++buf->st_count > SYMLOOP_MAX)
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{
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return -ELOOP;
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}
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/* If stat() fails, then there is a probleml with target of the
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/* stat() the target of the soft link. */
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ret = stat_recursive((FAR const char *)inode->u.i_link, buf);
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/* If stat() fails, then there is a problem with the target of the
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* symbolic link, but not with the symbolic link itself. We should
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* still report success, just with less information.
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*/
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if (ret < 0)
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{
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memset(buf, 0, sizeof(struct stat));
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RESET_BUF(buf);
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}
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/* And make sure that the caller knows that this really a symbolic link. */
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/* Make sure that the caller knows that this really a symbolic link. */
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buf->st_mode |= S_IFLNK;
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}
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@ -180,17 +209,13 @@ static inline int statroot(FAR struct stat *buf)
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{
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/* There is no inode associated with the fake root directory */
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memset(buf, 0, sizeof(struct stat));
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RESET_BUF(buf);
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buf->st_mode = S_IFDIR | S_IROTH | S_IRGRP | S_IRUSR;
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return OK;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: stat
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* Name: stat_recursive
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*
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* Returned Value:
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* Zero on success; -1 on failure with errno set:
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@ -205,34 +230,13 @@ static inline int statroot(FAR struct stat *buf)
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*
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****************************************************************************/
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int stat(FAR const char *path, FAR struct stat *buf)
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int stat_recursive(FAR const char *path, FAR struct stat *buf)
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{
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struct inode_search_s desc;
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FAR struct inode *inode;
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int ret = OK;
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int ret;
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/* Sanity checks */
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if (!path || !buf)
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{
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ret = EFAULT;
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goto errout;
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}
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if (!path[0])
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{
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ret = ENOENT;
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goto errout;
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}
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/* Check for the fake root directory (which has no inode) */
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if (strcmp(path, "/") == 0)
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{
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return statroot(buf);
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}
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/* Get an inode for this file */
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/* Get an inode for this path */
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SETUP_SEARCH(&desc, path, true);
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@ -273,7 +277,9 @@ int stat(FAR const char *path, FAR struct stat *buf)
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else
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#endif
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{
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/* The node is part of the root pseudo file system */
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/* The node is part of the root pseudo file system. This path may
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* recurse if soft links are supported in the pseudo file system.
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*/
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ret = statpseudo(inode, buf);
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}
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@ -304,3 +310,62 @@ errout:
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set_errno(ret);
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return ERROR;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: stat
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*
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* Returned Value:
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* Zero on success; -1 on failure with errno set:
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*
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* EACCES Search permission is denied for one of the directories in the
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* path prefix of path.
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* EFAULT Bad address.
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* ENOENT A component of the path path does not exist, or the path is an
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* empty string.
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* ENOMEM Out of memory
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* ENOTDIR A component of the path is not a directory.
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*
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****************************************************************************/
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int stat(FAR const char *path, FAR struct stat *buf)
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{
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int ret;
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/* Sanity checks */
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if (path == NULL || buf == NULL)
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{
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ret = EFAULT;
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goto errout;
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}
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if (*path == '\0')
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{
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ret = ENOENT;
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goto errout;
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}
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/* Check for the fake root directory (which has no inode) */
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if (strcmp(path, "/") == 0)
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{
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return statroot(buf);
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}
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/* The perform the stat() operation on the path. This is potentially
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* recursive if soft link support is enabled.
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*/
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#ifdef CONFIG_PSEUDOFS_SOFTLINKS
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buf->st_count = 0;
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#endif
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return stat_recursive(path, buf);
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errout:
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set_errno(ret);
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return ERROR;
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}
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@ -151,7 +151,7 @@
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/* Required for symbolic links */
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#define _POSIX_SYMLOOP_MAX 100
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#define _POSIX_SYMLOOP_MAX 8
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/* Required for POSIX timers.
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*
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@ -40,6 +40,8 @@
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <time.h>
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@ -125,6 +127,9 @@ struct stat
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time_t st_atime; /* Time of last access */
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time_t st_mtime; /* Time of last modification */
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time_t st_ctime; /* Time of last status change */
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#ifdef CONFIG_PSEUDOFS_SOFTLINKS
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uint16_t st_count; /* Used internally to limit traversal of links */
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#endif
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};
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/****************************************************************************
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