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i3c: dw: avoid shift-out-of-bounds when DAA assigns no devices

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On an empty bus ENTDAA assigns nothing, so cmd->rx_len (the count
of addresses left unassigned) equals master->maxdevs.

The GENMASK() index master->maxdevs - cmd->rx_len - 1 then becomes -1,
which trips up UBSAN. This happens every time on boot on a Gigabyte/AMD
server:

    UBSAN: shift-out-of-bounds in drivers/i3c/master/dw-i3c-master.c:905:12
    shift exponent 64 is too large for 64-bit type 'long unsigned int'
    CPU: 7 UID: 0 PID: 963 Comm: (udev-worker) Not tainted 7.0.11-200.fc44.x86_64 #1 PREEMPT(lazy)
    Hardware name: Giga Computing E163-Z34-AAH1-000/MZ33-DC1-000, BIOS R32_F45 04/01/2026
    Call Trace:
     <TASK>
     dump_stack_lvl+0x5d/0x80
     ubsan_epilogue+0x5/0x2b
     __ubsan_handle_shift_out_of_bounds.cold+0xd7/0x1ab
     dw_i3c_master_daa.cold+0x1b/0x96 [dw_i3c_master]
     i3c_master_do_daa_ext.part.0+0x3e/0xf0 [i3c]

Skip the mask when no new device was assigned.

Fixes: 1dd728f5d4 ("i3c: master: Add driver for Synopsys DesignWare IP")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260630172904.2662160-1-kuba@kernel.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
Jakub Kicinski
2026-06-30 10:29:04 -07:00
committed by Alexandre Belloni
parent e2bda39d7f
commit 038cf48b31
1 changed files with 9 additions and 1 deletions
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10
drivers/i3c/master/dw-i3c-master.c
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@@ -888,7 +888,15 @@ static int dw_i3c_master_daa(struct i3c_master_controller *m)
if (!wait_for_completion_timeout(&xfer->comp, XFER_TIMEOUT))
dw_i3c_master_dequeue_xfer(master, xfer);
newdevs = GENMASK(master->maxdevs - cmd->rx_len - 1, 0);
/*
* cmd->rx_len holds the number of addresses ENTDAA left unassigned.
* On an empty bus rx_len == maxdevs, so avoid GENMASK(-1, 0).
*/
if (cmd->rx_len >= master->maxdevs)
newdevs = 0;
else
newdevs = GENMASK(master->maxdevs - cmd->rx_len - 1, 0);
newdevs &= ~olddevs;
for (pos = 0; pos < master->maxdevs; pos++) {