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ibmasm: fix heap over-read in ibmasm_send_i2o_message()

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The ibmasm_send_i2o_message() function uses get_dot_command_size() to
compute the byte count for memcpy_toio(), but this value is derived from
user-controlled fields in the dot_command_header (command_size: u8,
data_size: u16) and is never validated against the actual allocation size.
A root user can write a small buffer with inflated header fields, causing
memcpy_toio() to read up to ~65 KB past the end of the allocation into
adjacent kernel heap, which is then forwarded to the service processor
over MMIO.

Silently clamping the copy size is not sufficient: if the header fields
claim a larger size than the buffer, the SP receives a dot command whose
own header is inconsistent with the I2O message length, which can cause
the SP to desynchronize. Reject such commands outright by returning
failure.

Validate command_size before calling get_mfa_inbound() to avoid leaking
an I2O message frame: reading INBOUND_QUEUE_PORT dequeues a hardware
frame from the controller's free pool, and returning without a
corresponding set_mfa_inbound() call would permanently exhaust it.

Additionally, clamp command_size to I2O_COMMAND_SIZE before the
memcpy_toio() so the MMIO write stays within the I2O message frame,
consistent with the clamping already performed by outgoing_message_size()
for the header field.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Tyllis Xu <LivelyCarpet87@gmail.com>
Link: https://patch.msgid.link/20260314165805.548293-1-LivelyCarpet87@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tyllis Xu
2026-03-14 11:58:05 -05:00
committed by Greg Kroah-Hartman
parent 0eb09f7374
commit 9aad71144f
1 changed files with 8 additions and 4 deletions
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12
drivers/misc/ibmasm/lowlevel.c
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@@ -19,17 +19,21 @@ static struct i2o_header header = I2O_HEADER_TEMPLATE;
int ibmasm_send_i2o_message(struct service_processor *sp)
{
u32 mfa;
unsigned int command_size;
size_t command_size;
struct i2o_message *message;
struct command *command = sp->current_command;
command_size = get_dot_command_size(command->buffer);
if (command_size > command->buffer_size)
return 1;
if (command_size > I2O_COMMAND_SIZE)
command_size = I2O_COMMAND_SIZE;
mfa = get_mfa_inbound(sp->base_address);
if (!mfa)
return 1;
command_size = get_dot_command_size(command->buffer);
header.message_size = outgoing_message_size(command_size);
header.message_size = outgoing_message_size((unsigned int)command_size);
message = get_i2o_message(sp->base_address, mfa);
memcpy_toio(&message->header, &header, sizeof(struct i2o_header));