https://github.com/torvalds/linux
Revision 4bfe6cce133cad82cea04490c308795275857782 authored by Jay Lang on 24 May 2020, 16:27:39 UTC, committed by Thomas Gleixner on 28 May 2020, 19:36:20 UTC
In the copy_process() routine called by _do_fork(), failure to allocate a PID (or further along in the function) will trigger an invocation to exit_thread(). This is done to clean up from an earlier call to copy_thread_tls(). Naturally, the child task is passed into exit_thread(), however during the process, io_bitmap_exit() nullifies the parent's io_bitmap rather than the child's. As copy_thread_tls() has been called ahead of the failure, the reference count on the calling thread's io_bitmap is incremented as we would expect. However, io_bitmap_exit() doesn't accept any arguments, and thus assumes it should trash the current thread's io_bitmap reference rather than the child's. This is pretty sneaky in practice, because in all instances but this one, exit_thread() is called with respect to the current task and everything works out. A determined attacker can issue an appropriate ioctl (i.e. KDENABIO) to get a bitmap allocated, and force a clone3() syscall to fail by passing in a zeroed clone_args structure. The kernel handles the erroneous struct and the buggy code path is followed, and even though the parent's reference to the io_bitmap is trashed, the child still holds a reference and thus the structure will never be freed. Fix this by tweaking io_bitmap_exit() and its subroutines to accept a task_struct argument which to operate on. Fixes: ea5f1cd7ab49 ("x86/ioperm: Remove bitmap if all permissions dropped") Signed-off-by: Jay Lang <jaytlang@mit.edu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable#@vger.kernel.org Link: https://lkml.kernel.org/r/20200524162742.253727-1-jaytlang@mit.edu
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Tip revision: 4bfe6cce133cad82cea04490c308795275857782 authored by Jay Lang on 24 May 2020, 16:27:39 UTC
x86/ioperm: Prevent a memory leak when fork fails
x86/ioperm: Prevent a memory leak when fork fails
Tip revision: 4bfe6cc
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arch | ||
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certs | ||
crypto | ||
drivers | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
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security | ||
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.clang-format | -rw-r--r-- | 15.8 KB |
.cocciconfig | -rw-r--r-- | 59 bytes |
.get_maintainer.ignore | -rw-r--r-- | 71 bytes |
.gitattributes | -rw-r--r-- | 62 bytes |
.gitignore | -rw-r--r-- | 1.7 KB |
.mailmap | -rw-r--r-- | 15.2 KB |
COPYING | -rw-r--r-- | 496 bytes |
CREDITS | -rw-r--r-- | 97.4 KB |
Kbuild | -rw-r--r-- | 1.3 KB |
Kconfig | -rw-r--r-- | 595 bytes |
MAINTAINERS | -rw-r--r-- | 539.4 KB |
Makefile | -rw-r--r-- | 60.3 KB |
README | -rw-r--r-- | 727 bytes |
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