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do_check_nonce: Don't free uninitialized memory on OOM

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If _dbus_string_init() fails, it doesn't guarantee that the string
is initialized to anything in particular. Worse, if
_dbus_string_init (&buffer) fails, p would never have been initialized
at all, due to the use of the short-circuiting || operator.

Signed-off-by: Simon McVittie <smcv@collabora.com>
Reviewed-by: Philip Withnall <withnall@endlessm.com>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=103597
(cherry picked from commit 0ea0e4b0fd)
This commit is contained in:
Simon McVittie 2017-11-06 19:09:51 +00:00
parent b5d1585b0f
commit 208af9a447
1 changed files with 14 additions and 0 deletions
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14
dbus/dbus-nonce.c
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@ -43,6 +43,20 @@ do_check_nonce (DBusSocket fd, const DBusString *nonce, DBusError *error)
nleft = 16;
/* This is a trick to make it safe to call _dbus_string_free on these
* strings during error unwinding, even if allocating memory for them
* fails. A constant DBusString is considered to be valid to "free",
* even though there is nothing to free (of course the free operation
* is trivial, because it does not own its own buffer); but
* unlike a mutable DBusString, initializing a constant DBusString
* cannot fail.
*
* We must successfully re-initialize the strings to be mutable before
* writing to them, of course.
*/
_dbus_string_init_const (&buffer, "");
_dbus_string_init_const (&p, "");
if ( !_dbus_string_init (&buffer)
|| !_dbus_string_init (&p) ) {
dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);