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| author | David Howells <dhowells@redhat.com> | 2006-09-27 10:50:19 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-09-27 17:26:14 +0200 |
| commit | d00c7b993712e4bb16d0012b35b654e40159b327 (patch) | |
| tree | 79f8fc60f8e41e054abc39b5d69e84d7a389777c /Documentation/nommu-mmap.txt | |
| parent | [PATCH] NOMMU: Check VMA protections (diff) | |
| download | linux-d00c7b993712e4bb16d0012b35b654e40159b327.tar.xz linux-d00c7b993712e4bb16d0012b35b654e40159b327.zip | |
[PATCH] NOMMU: Permit ptrace to ignore non-PROT_WRITE VMAs in NOMMU mode
Permit ptrace to modify a section that's non-shared but is marked
unwritable, such as is obtained by mapping the text segment of an ELF-FDPIC
executable binary with into a binary that's being ptraced[*].
[*] Under NOMMU conditions ptrace causes read-only MAP_PRIVATE mmaps to become
totally private copies because if a private mapping was actually shared
then the debugging setting breakpoints in it would potentially crash
other processes.
This is done by using the VM_MAYWRITE flag rather than the VM_WRITE flag
when deciding whether to permit a write.
Without this patch a debugger can't set breakpoints in the mapped text
sections of executables that are mapped read-only private, even if the
mmap() syscall has taken a private copy because PT_PTRACED is set.
In addition, VM_MAYREAD is used instead of VM_READ for similar reasons.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'Documentation/nommu-mmap.txt')
0 files changed, 0 insertions, 0 deletions