|author||Joshua Peraza <firstname.lastname@example.org>||Wed Oct 31 01:11:33 2018|
|committer||Commit Bot <email@example.com>||Wed Oct 31 23:35:50 2018|
Use a relative address in .note.crashpad.info The desc value in the note is now the offset of CRASHPAD_INFO_SYMBOL from desc. Making this note writable can trigger a linker error resulting in the binary embedding .note.crashpad.info to be rejected by the kernel during program loading. The error was observed with: GNU ld (GNU Binutils for Debian) 2.30 clang version 4.0.1-10 (tags/RELEASE_401/final) Debian 4.17.17-1rodete2 When the note is made writable, crashpad_snapshot_test contains two PT_LOAD segments which map to the same page. LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000258 0x0000000000000258 R 0x200000 LOAD 0x0000000000000258 0x0000000000000258 0x0000000000000258 0x00000000002b84d8 0x00000000002b8950 RWE 0x200000 Executing this binary with the execv system call triggers a segfault during program loading (an error can't be returned because the original process vm has already been discarded). I suspect (I haven't set up a debuggable kernel) the failure occurs while attempting to map the second load segment because its virtual address, 0x258, is in the same page as the first load segment. https://elixir.bootlin.com/linux/v4.17.17/source/fs/binfmt_elf.c#L380 The linker normally produces consecutive load segments where the second segment is loaded 0x200000 bytes after the first, which I think is the maximum expected page size. Modifying the test executable to load the second segment at 0x1258 (4096 byte page size) allows program loading to succeed (but of course crashes after control is given to it). Bug: crashpad:260 Change-Id: I2b9f1e66e98919138baef3da991a9710bd970dc4 Reviewed-on: https://chromium-review.googlesource.com/c/1292232 Reviewed-by: Scott Graham <firstname.lastname@example.org> Reviewed-by: Mark Mentovai <email@example.com> Commit-Queue: Joshua Peraza <firstname.lastname@example.org>
Crashpad is a crash-reporting system.
Crashpad’s source code is hosted in a Git repository at https://chromium.googlesource.com/crashpad/crashpad.