I need to somehow retrieve both real and effective UID and GID as well as the supplementary groups of a process, knowing only its PID.
The file fs/proc/array.c
uses the struct cred
for that purpose (p is struct task_struct *p
):
cred = get_task_cred(p);
However, I cannot find a way to retrieve such a struct in user-mode using the PID of another process.
Is there any way to get the information from user-mode (unix kernel 3.13)?
Information about processes is stored in proc filesystem where each process has its respective directory. The fields you're looking for are Uid:
and Gid:
which also contain effective UID/GID.
From the kernel documentation :
stat Process status
statm Process memory status information
status Process status in human readable form
However, from the same kernel documentation you can also find:
Uid Real, effective, saved set, and file system UIDs
Gid Real, effective, saved set, and file system GIDs
Since the file status
served from the proc filesystem is simply a text file, you can just go ahead and read the required information from there with any way you like, for example fscanf()
.
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