{"id":2223211,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2223211/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-i2c/patch/20260414172338.110830-2-bestswngs@gmail.com/","project":{"id":35,"url":"http://patchwork.ozlabs.org/api/1.1/projects/35/?format=json","name":"Linux I2C development","link_name":"linux-i2c","list_id":"linux-i2c.vger.kernel.org","list_email":"linux-i2c@vger.kernel.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260414172338.110830-2-bestswngs@gmail.com>","date":"2026-04-14T17:23:39","name":"[v2] i2c: stub: Reject I2C block transfers with invalid length","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"6436e673bee9e5761db014c2b212b23284ccbd73","submitter":{"id":92941,"url":"http://patchwork.ozlabs.org/api/1.1/people/92941/?format=json","name":"Weiming Shi","email":"bestswngs@gmail.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linux-i2c/patch/20260414172338.110830-2-bestswngs@gmail.com/mbox/","series":[{"id":499879,"url":"http://patchwork.ozlabs.org/api/1.1/series/499879/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-i2c/list/?series=499879","date":"2026-04-14T17:23:39","name":"[v2] i2c: stub: Reject I2C block transfers with invalid length","version":2,"mbox":"http://patchwork.ozlabs.org/series/499879/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2223211/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2223211/checks/","tags":{},"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-i2c@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=cJ5fLkQ+;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c0a:e001:db::12fc:5321; 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The existing check only clamps it to avoid\noverrunning the chip->words[256] register array, but does not validate\nit against I2C_SMBUS_BLOCK_MAX (32), which is the limit of the union\ni2c_smbus_data.block buffer (34 bytes total). The driver is a\ndevelopment/test tool (CONFIG_I2C_STUB=m, not built by default)\nthat must be loaded with a chip_addr= parameter.\n\nA local user with access to /dev/i2c-* can issue an I2C_SMBUS ioctl\nwith I2C_SMBUS_I2C_BLOCK_DATA and data->block[0] > 32, causing\nstub_xfer() to read or write past the end of the union\ni2c_smbus_data.block buffer:\n\n BUG: KASAN: stack-out-of-bounds in stub_xfer (drivers/i2c/i2c-stub.c:223)\n Read of size 1 at addr ffff88800abcfd92 by task exploit/81\n Call Trace:\n \n stub_xfer (drivers/i2c/i2c-stub.c:223)\n __i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:593)\n i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:536)\n i2cdev_ioctl_smbus (drivers/i2c/i2c-dev.c:391)\n i2cdev_ioctl (drivers/i2c/i2c-dev.c:478)\n __x64_sys_ioctl (fs/ioctl.c:583)\n do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)\n \n\nThe bug exists because i2c-stub implements .smbus_xfer directly,\nbypassing the I2C_SMBUS_BLOCK_MAX validation in\ni2c_smbus_xfer_emulated(). The I2C_SMBUS_BLOCK_DATA case in the same\nfunction correctly validates against I2C_SMBUS_BLOCK_MAX, but the\nI2C_SMBUS_I2C_BLOCK_DATA case does not.\n\nFix by rejecting transfers with data->block[0] == 0 or\ndata->block[0] > I2C_SMBUS_BLOCK_MAX with -EINVAL, consistent with\nboth the I2C_SMBUS_BLOCK_DATA case in the same function and the\nI2C_SMBUS_I2C_BLOCK_DATA validation in i2c_smbus_xfer_emulated().\n\nFixes: 4710317891e4 (\"i2c-stub: Implement I2C block support\")\nReported-by: Xiang Mei \nSigned-off-by: Weiming Shi \n---\nv2:\n - Also reject data->block[0] == 0 (suggested by Jean Delvare).\n\n drivers/i2c/i2c-stub.c | 5 +++++\n 1 file changed, 5 insertions(+)","diff":"diff --git a/drivers/i2c/i2c-stub.c b/drivers/i2c/i2c-stub.c\nindex fbb0db41b10e1..04314e3ed24c9 100644\n--- a/drivers/i2c/i2c-stub.c\n+++ b/drivers/i2c/i2c-stub.c\n@@ -214,6 +214,11 @@ static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,\n \t\t * We ignore banks here, because banked chips don't use I2C\n \t\t * block transfers\n \t\t */\n+\t\tif (data->block[0] == 0 ||\n+\t\t data->block[0] > I2C_SMBUS_BLOCK_MAX) {\n+\t\t\tret = -EINVAL;\n+\t\t\tbreak;\n+\t\t}\n \t\tif (data->block[0] > 256 - command)\t/* Avoid overrun */\n \t\t\tdata->block[0] = 256 - command;\n \t\tlen = data->block[0];\n","prefixes":["v2"]}