{"id":"AZL-103661","summary":"CVE-2026-93287 affecting package kernel 6.6.157.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ni2c: smbus: reject oversized block transfers in the common path\n\nThe SMBus block transfer length data-\u003eblock[0] is validated in\ni2c_smbus_xfer_emulated() but that check runs too late for tracepoints\nand is skipped entirely when the adapter provides a native smbus_xfer\nimplementation. This allows user-controlled oversized block lengths to\nreach tracepoint memcpy calls and driver callbacks unchecked.\n\nAdd an early validation in __i2c_smbus_xfer() that rejects block\ntransfers whose caller-supplied length is zero or exceeds\nI2C_SMBUS_BLOCK_MAX before any tracepoint fires or driver callback\nruns. data-\u003eblock[0] is filled in by the device on SMBus block reads,\nso the check is scoped to operations where the length is actually\nsupplied by the caller. This is consistent with the existing -EINVAL\nconvention in the emulated path and protects all downstream consumers\nat once: the smbus_write tracepoint, all native smbus_xfer driver\nimplementations, and the emulated path.\n\nTwo distinct bugs are fixed by this change:\n\nBug 1: smbus_write tracepoint OOB (include/trace/events/smbus.h)\n  trace_smbus_write() fires before any validation and copies\n  data-\u003eblock[0]+1 bytes into a 34-byte event buffer. With\n  block[0]=0xfe the tracepoint copies 255 bytes, overflowing by 221.\n\n BUG: KASAN: stack-out-of-bounds in trace_event_raw_event_smbus_write+0x27c/0x530\n Read of size 255 at addr ffff88800d98fcf8 by task poc_smbus/91\n Call Trace:\n  \u003cTASK\u003e\n  __asan_memcpy+0x23/0x80\n  trace_event_raw_event_smbus_write+0x27c/0x530\n  __i2c_smbus_xfer+0x43a/0xa40\n  i2c_smbus_xfer+0x19e/0x340\n  i2cdev_ioctl_smbus+0x38f/0x7f0\n  i2cdev_ioctl+0x35e/0x680\n  __x64_sys_ioctl+0x147/0x1e0\n  do_syscall_64+0xcf/0x15a0\n  entry_SYSCALL_64_after_hwframe+0x76/0x7e\n  \u003c/TASK\u003e\n\nBug 2: i2c-stub I2C_SMBUS_I2C_BLOCK_DATA OOB (drivers/i2c/i2c-stub.c)\n  stub_xfer() implements .smbus_xfer directly and only clamps\n  block[0] against 256-command, not I2C_SMBUS_BLOCK_MAX. With\n  block[0]=0xff and command=0 the loop accesses block[1+i] for\n  i up to 254, far past the 34-byte union.\n\n UBSAN: array-index-out-of-bounds in drivers/i2c/i2c-stub.c:223:44\n index 34 is out of range for type '__u8 [34]'\n Call Trace:\n  \u003cTASK\u003e\n  __ubsan_handle_out_of_bounds+0xd7/0x120\n  stub_xfer+0x1971/0x198f [i2c_stub]\n  __i2c_smbus_xfer+0x306/0xa40\n  i2c_smbus_xfer+0x19e/0x340\n  i2cdev_ioctl_smbus+0x38f/0x7f0\n  i2cdev_ioctl+0x35e/0x680\n  __x64_sys_ioctl+0x147/0x1e0\n  do_syscall_64+0xcf/0x15a0\n  entry_SYSCALL_64_after_hwframe+0x76/0x7e\n  \u003c/TASK\u003e\n\nBoth traces reproduced on v7.0-rc6+i2c/for-current with KASAN+UBSAN.","modified":"2026-09-25T14:16:23.942127246Z","published":"2026-09-24T17:17:09Z","upstream":["CVE-2026-93287"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-93287"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.157.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-103661.json"}}],"schema_version":"1.9.0"}