5.15-stable review patch. If anyone has any objections, please let me know.

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From: Desnes Nunes desnesn@redhat.com

commit 41e99fe2005182139b1058db71f0d241f8f0078c upstream.

A kernel memory leak was identified by the 'ioctl_sg01' test from Linux Test Project (LTP). The following bytes were mainly observed: 0x53425355.

When USB storage devices incorrectly skip the data phase with status data, the code extracts/validates the CSW from the sg buffer, but fails to clear it afterwards. This leaves status protocol data in srb's transfer buffer, such as the US_BULK_CS_SIGN 'USBS' signature observed here. Thus, this can lead to USB protocols leaks to user space through SCSI generic (/dev/sg*) interfaces, such as the one seen here when the LTP test requested 512 KiB.

Fix the leak by zeroing the CSW data in srb's transfer buffer immediately after the validation of devices that skip data phase.

Note: Differently from CVE-2018-1000204, which fixed a big leak by zero- ing pages at allocation time, this leak occurs after allocation, when USB protocol data is written to already-allocated sg pages.

Fixes: a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") Cc: stable stable@kernel.org Signed-off-by: Desnes Nunes desnesn@redhat.com Reviewed-by: Alan Stern stern@rowland.harvard.edu Link: https://patch.msgid.link/20251031043436.55929-1-desnesn@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/storage/transport.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)

--- a/drivers/usb/storage/transport.c +++ b/drivers/usb/storage/transport.c @@ -1204,7 +1204,23 @@ int usb_stor_Bulk_transport(struct scsi_ US_BULK_CS_WRAP_LEN && bcs->Signature == cpu_to_le32(US_BULK_CS_SIGN)) { + unsigned char buf[US_BULK_CS_WRAP_LEN]; + usb_stor_dbg(us, "Device skipped data phase\n"); + + /* + * Devices skipping data phase might leave CSW data in srb's + * transfer buffer. Zero it to prevent USB protocol leakage. + */ + sg = NULL; + offset = 0; + memset(buf, 0, sizeof(buf)); + if (usb_stor_access_xfer_buf(buf, + US_BULK_CS_WRAP_LEN, srb, &sg, + &offset, TO_XFER_BUF) != + US_BULK_CS_WRAP_LEN) + usb_stor_dbg(us, "Failed to clear CSW data\n"); + scsi_set_resid(srb, transfer_length); goto skipped_data_phase; }