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* [newlib-cygwin] Cygwin: fhandler_procsys::readdir: fix NtQueryDirectoryObject usage
@ 2021-08-19 19:17 Corinna Vinschen
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From: Corinna Vinschen @ 2021-08-19 19:17 UTC (permalink / raw)
To: cygwin-cvs
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=5036d447c54c41968ccd19a6294f69e4085d0143
commit 5036d447c54c41968ccd19a6294f69e4085d0143
Author: Corinna Vinschen <corinna@vinschen.de>
Date: Thu Aug 19 21:17:11 2021 +0200
Cygwin: fhandler_procsys::readdir: fix NtQueryDirectoryObject usage
As outlined in the previous patch, the non-atomicity of iterating
over a directory in the NT namespace via NtQueryDirectoryObject
one entry each, results in potential duplication of directory entries.
Fix this for fhandler_procsys::readdir as well by fetching the entire
dir inside fhandler_procsys::opendir, storing it in a buffer, and just
return buffer content from fhandler_procsys::readdir.
Fixes: 43f65cdd7dae ("fhandler_procsys.cc: New file.")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Diff:
---
winsup/cygwin/fhandler_procsys.cc | 82 +++++++++++++++++++++++++++------------
1 file changed, 58 insertions(+), 24 deletions(-)
diff --git a/winsup/cygwin/fhandler_procsys.cc b/winsup/cygwin/fhandler_procsys.cc
index f8abbe7c0..02741d0e9 100644
--- a/winsup/cygwin/fhandler_procsys.cc
+++ b/winsup/cygwin/fhandler_procsys.cc
@@ -309,59 +309,88 @@ fhandler_procsys::opendir (int fd)
UNICODE_STRING path;
OBJECT_ATTRIBUTES attr;
NTSTATUS status;
- HANDLE h;
+ HANDLE dir_hdl;
DIR *dir;
mk_unicode_path (&path);
InitializeObjectAttributes (&attr, &path, OBJ_CASE_INSENSITIVE, NULL, NULL);
- status = NtOpenDirectoryObject (&h, DIRECTORY_QUERY, &attr);
+ status = NtOpenDirectoryObject (&dir_hdl, DIRECTORY_QUERY, &attr);
if (!NT_SUCCESS (status))
{
__seterrno_from_nt_status (status);
return NULL;
}
+
+ void *dbi_buf = NULL;
+ ULONG size = 65536;
+ ULONG context = 0;
+ int iter;
+ for (iter = 0; iter <= 3; ++iter) /* Allows for a 512K buffer */
+ {
+ void *new_buf = realloc (dbi_buf, size);
+ if (!new_buf)
+ goto err;
+ dbi_buf = new_buf;
+ status = NtQueryDirectoryObject (dir_hdl, dbi_buf, size, FALSE, TRUE,
+ &context, NULL);
+ if (!NT_SUCCESS (status))
+ {
+ __seterrno_from_nt_status (status);
+ goto err;
+ }
+ if (status != STATUS_MORE_ENTRIES)
+ break;
+ size <<= 1;
+ }
+ if (iter > 3)
+ {
+ __seterrno_from_nt_status (STATUS_INSUFFICIENT_RESOURCES);
+ goto err;
+ }
if (!(dir = fhandler_virtual::opendir (fd)))
- NtClose (h);
- else
- dir->__handle = h;
+ goto err;
+ /* Note that dir->__handle points to the buffer, it does NOT contain an
+ actual handle! */
+ dir->__handle = dbi_buf;
+ /* dir->__d_internal contains the number of objects returned in the buffer. */
+ dir->__d_internal = context;
return dir;
+
+err:
+ NtClose (dir_hdl);
+ free (dbi_buf);
+ return NULL;
}
int
fhandler_procsys::readdir (DIR *dir, dirent *de)
{
- NTSTATUS status;
- struct fdbi
- {
- DIRECTORY_BASIC_INFORMATION dbi;
- WCHAR buf[2][NAME_MAX + 1];
- } f;
+ PDIRECTORY_BASIC_INFORMATION dbi;
int res = EBADF;
if (dir->__handle != INVALID_HANDLE_VALUE)
{
- BOOLEAN restart = dir->__d_position ? FALSE : TRUE;
- status = NtQueryDirectoryObject (dir->__handle, &f, sizeof f, TRUE,
- restart, (PULONG) &dir->__d_position,
- NULL);
- if (!NT_SUCCESS (status))
+ dbi = ((PDIRECTORY_BASIC_INFORMATION) dir->__handle);
+ dbi += dir->__d_position;
+ if (dir->__d_position >= (__int32_t) dir->__d_internal
+ || dbi->ObjectName.Length == 0)
res = ENMFILE;
else
{
- sys_wcstombs (de->d_name, NAME_MAX + 1, f.dbi.ObjectName.Buffer,
- f.dbi.ObjectName.Length / sizeof (WCHAR));
+ sys_wcstombs (de->d_name, NAME_MAX + 1, dbi->ObjectName.Buffer,
+ dbi->ObjectName.Length / sizeof (WCHAR));
de->d_ino = hash_path_name (get_ino (), de->d_name);
- if (RtlEqualUnicodeString (&f.dbi.ObjectTypeName, &ro_u_natdir,
- FALSE))
+ if (RtlEqualUnicodeString (&dbi->ObjectTypeName, &ro_u_natdir, FALSE))
de->d_type = DT_DIR;
- else if (RtlEqualUnicodeString (&f.dbi.ObjectTypeName, &ro_u_natsyml,
+ else if (RtlEqualUnicodeString (&dbi->ObjectTypeName, &ro_u_natsyml,
FALSE))
de->d_type = DT_LNK;
- else if (!RtlEqualUnicodeString (&f.dbi.ObjectTypeName, &ro_u_natdev,
+ else if (!RtlEqualUnicodeString (&dbi->ObjectTypeName, &ro_u_natdev,
FALSE))
de->d_type = DT_CHR;
else /* Can't nail down "Device" objects without further testing. */
de->d_type = DT_UNKNOWN;
+ ++dir->__d_position;
res = 0;
}
}
@@ -378,7 +407,12 @@ fhandler_procsys::telldir (DIR *dir)
void
fhandler_procsys::seekdir (DIR *dir, long pos)
{
- dir->__d_position = pos;
+ if (pos < 0)
+ dir->__d_position = 0;
+ else if (pos > (__int32_t) dir->__d_internal)
+ dir->__d_position = (__int32_t) dir->__d_internal;
+ else
+ dir->__d_position = pos;
}
int
@@ -386,7 +420,7 @@ fhandler_procsys::closedir (DIR *dir)
{
if (dir->__handle != INVALID_HANDLE_VALUE)
{
- NtClose (dir->__handle);
+ free (dir->__handle);
dir->__handle = INVALID_HANDLE_VALUE;
}
return fhandler_virtual::closedir (dir);
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