CVE-2026-63887

In the Linux kernel, the following vulnerability has been resolved:

scsi: target: iscsi: Bound iscsiencodetextoutput() appends to rspbuf

iscsiencodetext_output() concatenates "key=value\0" records into

login->rspbuf, an 8192-byte kzalloc(MAXKEYVALUEPAIRS) buffer

allocated in iscsitallocloginsetupbuffer(). The three sprintf() call

sites in this function (lines 1398, 1411, 1424 in v7.1-rc2) never check

the remaining buffer capacity:

*length += sprintf(output_buf, "%s=%s", er->key, er->value);

*length += 1;

output_buf = textbuf + *length;

The 8192-byte ceiling at iscsitargetcheckloginrequest() bounds the

input Login PDU payload, but a single PDU can carry up to 2048 minimal

four-byte "a=b\0" pairs, each unknown key expanding to a 16-byte

"a=NotUnderstood\0" output record via iscsiaddnotunderstood_response().

2048 * 16 = 32 KiB of output into an 8 KiB buffer, producing a ~24 KiB

heap overrun in the kmalloc-8k slab.

The fix introduces a static iscsiencodetext_record() helper that uses

snprintf() with a per-call bounds check against the remaining buffer,

and threads a u32 textbuf_size parameter through

iscsiencodetext_output(). Both call sites in

iscsitargethandlecsgzero() (PHASE_SECURITY) and

iscsitargethandlecsgone() (PHASE_OPERATIONAL) pass

MAXKEYVALUE_PAIRS. On overflow the encoder logs the condition, calls

iscsireleaseextra_responses() to drop queued records, and returns -1;

both caller sites now emit ISCSISTATUSCLSINITIATORERR /

ISCSILOGINSTATUSINITERR via iscsittxlogin_rsp() before returning,

so the initiator sees an explicit failed-login response rather than a

silent connection drop. (Prior to this patch only the PHASE_OPERATIONAL

caller did that; the PHASE_SECURITY caller is converted to the same

shape.)