In the Linux kernel, the following vulnerability has been resolved:
scsi: target: Bound PR-OUT TransportID parsing to the received buffer
core_scsi3_decode_spec_i_port() and core_scsi3_emulate_register_and_move()
hand the raw PERSISTENT RESERVE OUT parameter buffer to
target_parse_pr_out_transport_id() without telling it how many bytes are
valid. For an iSCSI TransportID (FORMAT CODE 01b),
iscsi_parse_pr_out_transport_id() locates the ",i,0x" ISID separator with
an unbounded strstr() (and on the error path prints the name with a further
unbounded "%s"). An initiator can submit a TransportID whose iSCSI name
contains neither a ",i,0x" substring nor a NUL terminator, filling the
parameter list to its end, so the scan runs off the end of the buffer.
When the parameter list spans more than one page the buffer is a multi-page
vmap (transport_kmap_data_sg()), so the over-read walks into the trailing
vmalloc guard page and oopses (KASAN: vmalloc-out-of-bounds in strstr). It
is reachable by any fabric that delivers a PR OUT to a device exported
through an iSCSI TPG, including a guest via vhost-scsi.
Pass the number of received bytes down to the parser and validate the iSCSI
TransportID's own self-described length (ADDITIONAL LENGTH + 4) once, up
front: reject it if it is below the spc4r17 minimum or larger than the
received buffer, then bound the separator search, the ISID walk and the
name copy by that length. This is the length check the callers already
perform after the parse (core_scsi3_decode_spec_i_port() compares tid_len
against tpdl, core_scsi3_emulate_register_and_move() validates it against
data_length), moved ahead of the scan. Also drop the unbounded "%s" of the
unterminated name.
Add per-format explicit name-length checks before copying into i_str,
rather than silently truncating with min_t: for FORMAT CODE 00b reject if
the descriptor body (tid_len - 4 bytes) cannot fit in
i_str[TRANSPORT_IQN_LEN]; for FORMAT CODE 01b reject if the name portion
(from &buf[4] up to the separator) cannot fit. Both checks make the bounds
intent explicit at each format branch.
While here, also reject a FORMAT CODE 01b TransportID whose ",i,0x"
separator sits at the very end of the descriptor: that leaves an empty ISID
and points the returned port nexus pointer at buf + tid_len, one past the
descriptor, which the registration code (__core_scsi3_locate_pr_reg(),
__core_scsi3_alloc_registration()) then dereferences as the ISID string --
the same over-read of the parameter buffer for a malformed descriptor.
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 9.8
AV:N - The bug is triggered by a PERSISTENT RESERVE OUT SCSI command delivered over the LIO iSCSI target fabric (TCP/3260); remote initiators reach iscsi_parse_pr_out_transport_id() after login and normal SCSI command processing, and the fix commit notes the same path via vhost-scsi-backed exports.
AC:L - An attacker fully controls the PR-OUT parameter list and can reliably supply a FORMAT CODE 01b iSCSI TransportID without a ",i,0x" separator or NUL terminator and size it past one page so strstr() over-reads into the vmalloc guard page; no races or victim-specific memory layout are required.
PR:N - Exploitation requires only completing iSCSI login to an exported LUN as any initiator client, not host administrator privileges; LIO demo mode auto-provisions initiator ACLs and many storage appliances expose iSCSI targets to the network without mapping this to elevated OS credentials.
UI:N - No end-user or administrator action beyond normal automated iSCSI target operation is needed; a remote initiator can send the malicious PR OUT command directly once a session to the LUN exists.
S:U - The flaw corrupts or reads kernel memory and crashes the target host kernel within the same kernel security boundary; it does not by itself cross a VM, container, or IOMMU isolation boundary to another authority.
C:H - Unbounded strstr() and an unbounded %s on the error path perform out-of-bounds reads past the received PR-OUT buffer, potentially disclosing adjacent kernel memory before the fault, matching CVSS guidance for out-of-bounds reads beyond a few bytes.
I:H - A malformed TransportID can leave the ISID pointer one byte past the descriptor so subsequent registration code dereferences out of bounds, and the ISID normalization loop can write with tolower() beyond the buffer, giving a memory-corruption primitive in kernel context.
A:H - The over-read into a multi-page vmalloc mapping hits the guard page and triggers a KASAN vmalloc-out-of-bounds fault and kernel oops, remotely denying service to the host and all consumers of the iSCSI target.
| Attack Vector |
Network |
Scope |
Unchanged |
| Attack Complexity |
Low |
Confidentiality Impact |
High |
| Privileges Required |
None |
Integrity Impact |
High |
| User Interaction |
None |
Availability Impact |
High |
AV:N - The bug is triggered by a PERSISTENT RESERVE OUT SCSI command delivered over the LIO iSCSI target fabric (TCP/3260); remote initiators reach iscsi_parse_pr_out_transport_id() after login and normal SCSI command processing, and the fix commit notes the same path via vhost-scsi-backed exports.
AC:L - An attacker fully controls the PR-OUT parameter list and can reliably supply a FORMAT CODE 01b iSCSI TransportID without a ",i,0x" separator or NUL terminator and size it past one page so strstr() over-reads into the vmalloc guard page; no races or victim-specific memory layout are required.
PR:N - Exploitation requires only completing iSCSI login to an exported LUN as any initiator client, not host administrator privileges; LIO demo mode auto-provisions initiator ACLs and many storage appliances expose iSCSI targets to the network without mapping this to elevated OS credentials.
UI:N - No end-user or administrator action beyond normal automated iSCSI target operation is needed; a remote initiator can send the malicious PR OUT command directly once a session to the LUN exists.
S:U - The flaw corrupts or reads kernel memory and crashes the target host kernel within the same kernel security boundary; it does not by itself cross a VM, container, or IOMMU isolation boundary to another authority.
C:H - Unbounded strstr() and an unbounded %s on the error path perform out-of-bounds reads past the received PR-OUT buffer, potentially disclosing adjacent kernel memory before the fault, matching CVSS guidance for out-of-bounds reads beyond a few bytes.
I:H - A malformed TransportID can leave the ISID pointer one byte past the descriptor so subsequent registration code dereferences out of bounds, and the ISID normalization loop can write with tolower() beyond the buffer, giving a memory-corruption primitive in kernel context.
A:H - The over-read into a multi-page vmalloc mapping hits the guard page and triggers a KASAN vmalloc-out-of-bounds fault and kernel oops, remotely denying service to the host and all consumers of the iSCSI target.
CVSS 3.1