| From | Jann Horn <> | Date | Wed, 26 Feb 2020 21:29:18 +0100 | Subject | Re: [RFC PATCH v14 05/10] fs,landlock: Support filesystem access-control |
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On Mon, Feb 24, 2020 at 5:03 PM Mickaël Salaün <mic@digikod.net> wrote: > +static inline u32 get_mem_access(unsigned long prot, bool private) > +{ > + u32 access = LANDLOCK_ACCESS_FS_MAP; > + > + /* Private mapping do not write to files. */ > + if (!private && (prot & PROT_WRITE)) > + access |= LANDLOCK_ACCESS_FS_WRITE; > + if (prot & PROT_READ) > + access |= LANDLOCK_ACCESS_FS_READ; > + if (prot & PROT_EXEC) > + access |= LANDLOCK_ACCESS_FS_EXECUTE; > + return access; > +}
When I do the following, is landlock going to detect that the mmap() is a read access, or is it incorrectly going to think that it's neither read nor write?
$ cat write-only.c #include <fcntl.h> #include <sys/mman.h> #include <stdio.h> int main(void) { int fd = open("/etc/passwd", O_RDONLY); char *ptr = mmap(NULL, 0x1000, PROT_WRITE, MAP_PRIVATE, fd, 0); printf("'%.*s'\n", 4, ptr); } $ gcc -o write-only write-only.c -Wall $ ./write-only 'root' $
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