cbcvebase.
CVE-2021-47505
published 2024-05-24

CVE-2021-47505: In the Linux kernel, the following vulnerability has been resolved: aio: fix use-after-free due to missing POLLFREE handling signalfd_poll() and binder_poll()…

PriorityP340high7.8CVSS 3.1
AVLACLPRLUINSUCHIHAH
EPSS
0.25%
16.8th percentile
In the Linux kernel, the following vulnerability has been resolved: aio: fix use-after-free due to missing POLLFREE handling signalfd_poll() and binder_poll() are special in that they use a waitqueue whose lifetime is the current task, rather than the struct file as is normally the case. This is okay for blocking polls, since a blocking poll occurs within one task; however, non-blocking polls require another solution. This solution is for the queue to be cleared before it is freed, by sending a POLLFREE notification to all waiters. Unfortunately, only eventpoll handles POLLFREE. A second type of non-blocking poll, aio poll, was added in kernel v4.18, and it doesn't handle POLLFREE. This allows a use-after-free to occur if a signalfd or binder fd is polled with aio poll, and the waitqueue gets freed. Fix this by making aio poll handle POLLFREE. A patch by Ramji Jiyani (https://lore.kernel.org/r/[email protected]) tried to do this by making aio_poll_wake() always complete the request inline if POLLFREE is seen. However, that solution had two bugs. First, it introduced a deadlock, as it unconditionally locked the aio context while holding the waitqueue lock, which inverts the normal locking order. Second, it didn't consider that POLLFREE notifications are missed while the request has been temporarily de-queued. The second problem was solved by my previous patch. This patch then properly fixes the use-after-free by handling POLLFREE in a deadlock-free way. It does this by taking advantage of the fact that freeing of the waitqueue is RCU-delayed, similar to what eventpoll does.

Affected

16 ranges
VendorProductVersion rangeFixed in
debianlinux< linux 5.15.15-1 (bookworm)linux 5.15.15-1 (bookworm)
linuxlinux——
linuxlinux>= 2c14fa838cbefc23cf1c73ca167ed85b274b2913 < 321fba81ec034f88aea4898993c1bf15605c023f321fba81ec034f88aea4898993c1bf15605c023f
linuxlinux>= 2c14fa838cbefc23cf1c73ca167ed85b274b2913 < 4105e6a128e8a98455dfc9e6dbb2ab0c33c4497f4105e6a128e8a98455dfc9e6dbb2ab0c33c4497f
linuxlinux>= 2c14fa838cbefc23cf1c73ca167ed85b274b2913 < 47ffefd88abfffe8a040bcc1dd0554d4ea6f768947ffefd88abfffe8a040bcc1dd0554d4ea6f7689
linuxlinux>= 2c14fa838cbefc23cf1c73ca167ed85b274b2913 < 60d311f9e6381d779d7d53371f87285698ecee2460d311f9e6381d779d7d53371f87285698ecee24
linuxlinux>= 2c14fa838cbefc23cf1c73ca167ed85b274b2913 < 50252e4b5e989ce64555c7aef7516bdefc2fea7250252e4b5e989ce64555c7aef7516bdefc2fea72
linuxlinux_kernel——
linuxlinux_kernel>= 0 < 5.10.92-15.10.92-1
linuxlinux_kernel>= 0 < 5.15.15-15.15.15-1
linuxlinux_kernel>= 0 < 5.15.15-15.15.15-1
linuxlinux_kernel>= 0 < 5.15.15-15.15.15-1
linuxlinux_kernel>= 4.18 < 4.19.2214.19.221
linuxlinux_kernel>= 4.20 < 5.4.1655.4.165
linuxlinux_kernel>= 5.11 < 5.15.85.15.8
linuxlinux_kernel>= 5.5 < 5.10.855.10.85

CVSS provenance

nvdv3.17.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
osv7.8HIGH
vendor_debian7.8HIGH
vendor_redhat7.8HIGH
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