rtc: ac100: Fix clock provider use-after-free on probe failure
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 6.12.113, 6.18.56, 7.2.10
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
In the Linux kernel, the following vulnerability has been resolved: rtc: ac100: Fix clock provider use-after-free on probe failure ac100_rtc_register_clks() registers the RTC-32k clock with clk_hw_register_fixed_rate() and the clock provider with of_clk_add_hw_provider(). Neither is device managed, and both are released only from ac100_rtc_remove(). The driver core does not call remove() when probe() fails: really_probe() reaches probe_failed below the device_remove() call and goes straight to releasing the device's managed resources. ac100_rtc_probe() ends with return devm_rtc_register_device(chip->rtc); so if that fails after the clocks have been registered, the provider is left on the global of_clk_providers list holding chip->clk_data, which was allocated with devm_kzalloc() and is freed while probe() unwinds. A later lookup on this device tree node then reads freed memory in of_clk_hw_onecell_get(). Consumers that do exactly that exist in tree: the wifi power sequence nodes on sun8i-a83t-bananapi-m3 and sun8i-a83t-cubietruck-plus take <&ac100_rtc 1>, and the sun9i-a80 boards route osc32k through <&ac100_rtc 0>. The window is narrow, as devm_rtc_register_device() can only fail with -ENOMEM here, but the provider is left dangling whenever it does. The RTC-32k clock is leaked on the same path. Since clk_core_lookup() searches a global list that is not scoped per device, __clk_register() rejects the duplicate name with -EEXIST, so the leak also makes a later probe of the same device fail. The error path that returns -EINVAL when the ADDA 4M parent clock cannot be found leaks the RTC-32k clock in the same way. No provider has been registered at that point, so that one is a leak rather than a use-after-free. Register both with devm_clk_hw_register_fixed_rate() and devm_of_clk_add_hw_provider() so that they are released whenever the device goes away, on a failed probe as well as on unbind. Devres releases in reverse order of acquisition, so the provider is removed before chip->clk_data is freed, and the clkout children are now unregistered before their parent rather than after it. ac100_rtc_unregister_clks() and the remove callback then have nothing left to do and are removed.
Timeline
- CVE published
- Record last updated
Affected versions
- Linux Linux
From d00a18a42c1483924de086ddfb0efe8da1dba3ac · fixed in 12bcd20d76703ee2baf52224d287b7fea096b12f; From d00a18a42c1483924de086ddfb0efe8da1dba3ac · fixed in 9cff19ddd7f90c1f572a0f83cfc41de8f8dcbcd8; From d00a18a42c1483924de086ddfb0efe8da1dba3ac · fixed in 55ca60ba336632349f7c4585d22ba74ae355b7ce; From d00a18a42c1483924de086ddfb0efe8da1dba3ac · fixed in fcf0b58e976e83adf246b014518e49c662b96f5e
- Linux Linux
4.9
- KernelLinux
From 4.9.0 · fixed in 6.12.113; From 6.13.0 · fixed in 6.18.56; From 6.19.0 · fixed in 7.2.10