Commit 82aec772 authored by Jakub Kicinski's avatar Jakub Kicinski Committed by Paolo Abeni
Browse files

netconsole: avoid OOB reads, msg is not nul-terminated 



msg passed to netconsole from the console subsystem is not guaranteed
to be nul-terminated. Before recent
commit 7eab73b1 ("netconsole: convert to NBCON console infrastructure")
the message would be placed in printk_shared_pbufs, a static global
buffer, so KASAN had harder time catching OOB accesses. Now we see:

    printk: console [netcon_ext0] enabled
    BUG: KASAN: slab-out-of-bounds in string+0x1f7/0x240
    Read of size 1 at addr ffff88813b6d4c00 by task pr/netcon_ext0/594

    CPU: 65 UID: 0 PID: 594 Comm: pr/netcon_ext0 Not tainted 6.19.0-11754-g4246fd6547c9
    Call Trace:
     kasan_report+0xe4/0x120
     string+0x1f7/0x240
     vsnprintf+0x655/0xba0
     scnprintf+0xba/0x120
     netconsole_write+0x3fe/0xa10
     nbcon_emit_next_record+0x46e/0x860
     nbcon_kthread_func+0x623/0x750

    Allocated by task 1:
     nbcon_alloc+0x1ea/0x450
     register_console+0x26b/0xe10
     init_netconsole+0xbb0/0xda0

    The buggy address belongs to the object at ffff88813b6d4000
                which belongs to the cache kmalloc-4k of size 4096
    The buggy address is located 0 bytes to the right of
                allocated 3072-byte region [ffff88813b6d4000, ffff88813b6d4c00)

Fixes: c62c0a17 ("netconsole: Append kernel version to message")
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260219195021.2099699-1-kuba@kernel.org


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent bae8a5d2

drivers/net/netconsole.c

+2 −1
Original line number Diff line number Diff line
@@ -1679,7 +1679,8 @@ static void send_msg_no_fragmentation(struct netconsole_target *nt, 
	if (release_len) {

		release = init_utsname()->release;



		scnprintf(nt->buf, MAX_PRINT_CHUNK, "%s,%s", release, msg);

		scnprintf(nt->buf, MAX_PRINT_CHUNK, "%s,%.*s", release,

			  msg_len, msg);

		msg_len += release_len;

	} else {

		memcpy(nt->buf, msg, msg_len);