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Cygwin: fhandler_procsys::readdir: fix NtQueryDirectoryObject usage

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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>
This commit is contained in:
Corinna Vinschen 2021-08-19 21:17:11 +02:00
parent 2f05de4dbf
commit 5036d447c5
1 changed files with 58 additions and 24 deletions
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80
winsup/cygwin/fhandler_procsys.cc
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@ -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;
}
}
@ -378,6 +407,11 @@ fhandler_procsys::telldir (DIR *dir)
void
fhandler_procsys::seekdir (DIR *dir, long 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;
}
@ -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);