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e2dc9bf3f5
Instead of loading a binary blob into a temporary file with shmem_kernel_file_setup load a binary blob into a temporary tmpfs filesystem. This means that the blob can be stored in an init section and discared, and it means the binary blob will have a filename so can be executed normally. The only tricky thing about this code is that in the helper function blob_to_mnt __fput_sync is used. That is because a file can not be executed if it is still open for write, and the ordinary delayed close for kernel threads does not happen soon enough, which causes the following exec to fail. The function umd_load_blob is not called with any locks so this should be safe. Executing the blob normally winds up correcting several problems with the user mode driver code discovered by Tetsuo Handa[1]. By passing an ordinary filename into the exec, it is no longer necessary to figure out how to turn a O_RDWR file descriptor into a properly referende counted O_EXEC file descriptor that forbids all writes. For path based LSMs there are no new special cases. [1] https://lore.kernel.org/linux-fsdevel/2a8775b4-1dd5-9d5c-aa42-9872445e0942@i-love.sakura.ne.jp/ v1: https://lkml.kernel.org/r/87d05mf0j9.fsf_-_@x220.int.ebiederm.org v2: https://lkml.kernel.org/r/87wo3p4p35.fsf_-_@x220.int.ebiederm.org Link: https://lkml.kernel.org/r/20200702164140.4468-8-ebiederm@xmission.com Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Alexei Starovoitov <ast@kernel.org> Tested-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
34 lines
774 B
C
34 lines
774 B
C
#ifndef __LINUX_USERMODE_DRIVER_H__
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#define __LINUX_USERMODE_DRIVER_H__
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#include <linux/umh.h>
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#include <linux/path.h>
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#ifdef CONFIG_BPFILTER
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void __exit_umh(struct task_struct *tsk);
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static inline void exit_umh(struct task_struct *tsk)
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{
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if (unlikely(tsk->flags & PF_UMH))
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__exit_umh(tsk);
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}
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#else
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static inline void exit_umh(struct task_struct *tsk)
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{
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}
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#endif
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struct umd_info {
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const char *driver_name;
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struct file *pipe_to_umh;
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struct file *pipe_from_umh;
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struct list_head list;
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void (*cleanup)(struct umd_info *info);
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struct path wd;
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pid_t pid;
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};
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int umd_load_blob(struct umd_info *info, const void *data, size_t len);
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int umd_unload_blob(struct umd_info *info);
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int fork_usermode_driver(struct umd_info *info);
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#endif /* __LINUX_USERMODE_DRIVER_H__ */
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