mirror of
https://github.com/torvalds/linux.git
synced 2026-05-12 16:18:45 +02:00
ae88a5d2f2
Reproducer available at [1].
The ATM send path (sendmsg -> vcc_sendmsg -> sigd_send) reads the vcc
pointer from msg->vcc and uses it directly without any validation. This
pointer comes from userspace via sendmsg() and can be arbitrarily forged:
int fd = socket(AF_ATMSVC, SOCK_DGRAM, 0);
ioctl(fd, ATMSIGD_CTRL); // become ATM signaling daemon
struct msghdr msg = { .msg_iov = &iov, ... };
*(unsigned long *)(buf + 4) = 0xdeadbeef; // fake vcc pointer
sendmsg(fd, &msg, 0); // kernel dereferences 0xdeadbeef
In normal operation, the kernel sends the vcc pointer to the signaling
daemon via sigd_enq() when processing operations like connect(), bind(),
or listen(). The daemon is expected to return the same pointer when
responding. However, a malicious daemon can send arbitrary pointer values.
Fix this by introducing find_get_vcc() which validates the pointer by
searching through vcc_hash (similar to how sigd_close() iterates over
all VCCs), and acquires a reference via sock_hold() if found.
Since struct atm_vcc embeds struct sock as its first member, they share
the same lifetime. Therefore using sock_hold/sock_put is sufficient to
keep the vcc alive while it is being used.
Note that there may be a race with sigd_close() which could mark the vcc
with various flags (e.g., ATM_VF_RELEASED) after find_get_vcc() returns.
However, sock_hold() guarantees the memory remains valid, so this race
only affects the logical state, not memory safety.
[1]: https://gist.github.com/mrpre/1ba5949c45529c511152e2f4c755b0f3
Fixes:
|
||
|---|---|---|
| .. | ||
| addr.c | ||
| addr.h | ||
| atm_misc.c | ||
| atm_sysfs.c | ||
| br2684.c | ||
| clip.c | ||
| common.c | ||
| common.h | ||
| ioctl.c | ||
| Kconfig | ||
| lec_arpc.h | ||
| lec.c | ||
| lec.h | ||
| Makefile | ||
| mpc.c | ||
| mpc.h | ||
| mpoa_caches.c | ||
| mpoa_caches.h | ||
| mpoa_proc.c | ||
| pppoatm.c | ||
| proc.c | ||
| protocols.h | ||
| pvc.c | ||
| raw.c | ||
| resources.c | ||
| resources.h | ||
| signaling.c | ||
| signaling.h | ||
| svc.c | ||