From 51cfe54f815ae175c7d1126b983d4d7c89715004 Mon Sep 17 00:00:00 2001 From: Dmitry Torokhov Date: Tue, 4 Aug 2026 22:08:54 -0700 Subject: [PATCH] Input: rmi_smbus - fix out-of-bounds read in rmi_smb_write_block() When chunking writes into SMBus blocks in rmi_smb_write_block(), the loop calculates block_len using the original total length (len) instead of the remaining length (cur_len). If len is greater than 32 bytes (SMB_MAX_COUNT), block_len remains 32 for every iteration, even on the final partial chunk where fewer than 32 bytes remain. This causes smb_block_write() to read 32 bytes from the advanced data buffer pointer, reading past the end of the input buffer. Fix this by calculating block_len using cur_len and advancing the buffer and address pointers by block_len. Fixes: 82264d0cf7ae ("Input: synaptics-rmi4 - add SMBus support") Cc: stable@vger.kernel.org Reported-by: sashiko-bot@kernel.org Assisted-by: LLM Link: https://patch.msgid.link/anLFSMKSoKyyZ272@google.com Signed-off-by: Dmitry Torokhov --- drivers/input/rmi4/rmi_smbus.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/input/rmi4/rmi_smbus.c b/drivers/input/rmi4/rmi_smbus.c index 3160714a514a..8b61c2382297 100644 --- a/drivers/input/rmi4/rmi_smbus.c +++ b/drivers/input/rmi4/rmi_smbus.c @@ -140,7 +140,7 @@ static int rmi_smb_write_block(struct rmi_transport_dev *xport, u16 rmiaddr, u8 commandcode; struct rmi_smb_xport *rmi_smb = container_of(xport, struct rmi_smb_xport, xport); - int cur_len = (int)len; + size_t cur_len = len; mutex_lock(&rmi_smb->page_mutex); @@ -148,7 +148,7 @@ static int rmi_smb_write_block(struct rmi_transport_dev *xport, u16 rmiaddr, /* * break into 32 bytes chunks to write get command code */ - int block_len = min_t(int, len, SMB_MAX_COUNT); + int block_len = min_t(size_t, cur_len, SMB_MAX_COUNT); retval = rmi_smb_get_command_code(xport, rmiaddr, block_len, false, &commandcode); @@ -161,9 +161,9 @@ static int rmi_smb_write_block(struct rmi_transport_dev *xport, u16 rmiaddr, goto exit; /* prepare to write next block of bytes */ - cur_len -= SMB_MAX_COUNT; - databuff += SMB_MAX_COUNT; - rmiaddr += SMB_MAX_COUNT; + cur_len -= block_len; + databuff += block_len; + rmiaddr += block_len; } exit: mutex_unlock(&rmi_smb->page_mutex);