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CVE PROGRAM SOURCE RECORD7.8 High

CVE-2026-72135

tpm: Make the TPM character devices non-seekable

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: tpm: Make the TPM character devices non-seekable The TPM character devices expose a sequential command/response interface, but their open handlers leave FMODE_PREAD and FMODE_PWRITE enabled. After a command leaves a response pending, pread(fd, buf, 16, 0x1400) passes 0x1400 as *off to tpm_common_read(). The transfer length is bounded by response_length, but the offset is used unchecked when forming data_buffer + *off. A sufficiently large offset therefore causes an out-of-bounds heap read through copy_to_user() and, if the copy succeeds, an out-of-bounds zero-write through the following memset(). Positional I/O does not provide coherent semantics for this interface. An arbitrary pread offset cannot represent how much of a response has been consumed sequentially. The write callback always stores a command at the start of data_buffer, while pwrite() does not update file->f_pos and can leave the sequential read cursor stale. Call nonseekable_open() from both open handlers. This removes FMODE_PREAD and FMODE_PWRITE, causing positional reads and writes to fail with -ESPIPE before reaching the TPM callbacks, and explicitly marks the files non-seekable. Normal read() and write() continue to use the existing sequential f_pos cursor, leaving the response state machine unchanged. Tested on Linux 6.12 with KASAN and a swtpm TPM2 device: - sequential partial reads returned the complete response - pread() and preadv() with offset 0x1400 returned -ESPIPE - pwrite() and pwritev() with offset zero returned -ESPIPE - the pending response remained intact after the rejected operations - a subsequent normal command/response cycle completed normally - no KASAN report was produced.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 9488585b21bef0df1217e510c7134905d1d376a7 to < ed0ffc2c016629e40ba041ed0424a772d8b02e2caffected
  • 9488585b21bef0df1217e510c7134905d1d376a7 to < 232dcf908eb7eb9d8046a9597975caf44270966eaffected
  • 9488585b21bef0df1217e510c7134905d1d376a7 to < dda695fab5e21f923d29e8cb01df256468ddfbd1affected
  • 9488585b21bef0df1217e510c7134905d1d376a7 to < 9c513dabd4540f811585a2087f23069767a284daaffected
  • 9488585b21bef0df1217e510c7134905d1d376a7 to < 21a13f932972bc9836f58c44fcd47c62abdecd95affected
  • 9488585b21bef0df1217e510c7134905d1d376a7 to < ada4b9a5087ea7f30dd8e4c6411a4fb6547eb1edaffected
  • 9488585b21bef0df1217e510c7134905d1d376a7 to < 947b773caaa548672184df025271b29bdc80b0f1affected
  • 9488585b21bef0df1217e510c7134905d1d376a7 to < f20d61c22bcaf172d6790b6500e3838e532e71c8affected

Linux Linux

Default version status: affected

  • 5.0affected
  • 0 to < 5.0unaffected
  • 5.10.261 to ≤ 5.10.*unaffected
  • 5.15.212 to ≤ 5.15.*unaffected
  • 6.1.178 to ≤ 6.1.*unaffected
  • 6.6.145 to ≤ 6.6.*unaffected
  • 6.12.97 to ≤ 6.12.*unaffected
  • 6.18.40 to ≤ 6.18.*unaffected
  • 7.1.5 to ≤ 7.1.*unaffected
  • 7.2 to ≤ *unaffected

References