[PATCH] core-dumping unreadable binaries via PT_INTERP
Proposed patch to fix #5 in
http://www.isec.pl/vulnerabilities/isec-0017-binfmt_elf.txt
aka
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2004-1073
To reproduce, do
* grab poc at the end of advisory.
* add line "eph.p_memsz = 4096;" after "eph.p_filesz = 4096;"
where first "4096" is something equal to or greater than 4096.
* ./poc /usr/bin/sudo && ls -l
Here I get with 2.6.20-rc5:
-rw------- 1 ad ad 102400 2007-01-15 19:17 core
---s--x--x 2 root root 101820 2007-01-15 19:15 /usr/bin/sudo
Check for MAY_READ like binfmt_misc.c does.
Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 6e6d456..a4d933a 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -234,6 +234,14 @@
goto error;
}
+ /*
+ * If the binary is not readable then enforce
+ * mm->dumpable = 0 regardless of the interpreter's
+ * permissions.
+ */
+ if (file_permission(interpreter, MAY_READ) < 0)
+ bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
+
retval = kernel_read(interpreter, 0, bprm->buf,
BINPRM_BUF_SIZE);
if (retval < 0)