Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH v5 06/12] S.A.R.A.: WX protection | Date | Mon, 8 Jul 2019 12:42:15 +0000 |
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From: Salvatore Mesoraca > Sent: 06 July 2019 11:55 ... > Executable MMAP prevention works by preventing any new executable > allocation after the dynamic libraries have been loaded. It works under the > assumption that, when the dynamic libraries have been finished loading, the > RELRO section will be marked read only.
What about writing to the file of a dynamic library after it is loaded but before it is faulted it (or after evicting it from the I$).
... > +#define find_relro_section(ELFH, ELFP, FILE, RELRO, FOUND) do { \ > + unsigned long i; \ > + int _tmp; \ > + loff_t _pos = 0; \ > + if (ELFH.e_type == ET_DYN || ELFH.e_type == ET_EXEC) { \ > + for (i = 0; i < ELFH.e_phnum; ++i) { \ > + _pos = ELFH.e_phoff + i*sizeof(ELFP); \ > + _tmp = kernel_read(FILE, &ELFP, sizeof(ELFP), \ > + &_pos); \ > + if (_tmp != sizeof(ELFP)) \ > + break; \ > + if (ELFP.p_type == PT_GNU_RELRO) { \ > + RELRO = ELFP.p_offset >> PAGE_SHIFT; \ > + FOUND = true; \ > + break; \ > + } \ > + } \ > + } \ > +} while (0)
This is big for a #define. Since it contains kernel_read() it can't really matter if it is a real function.
David
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