From 1fb844961818ce94e782acf6a96b92dc2303553b Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Fri, 26 Jan 2007 00:57:16 -0800 Subject: [PATCH] [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/binfmt_elf.c | 9 +++++++++ fs/binfmt_elf_fdpic.c | 8 ++++++++ 2 files changed, 17 insertions(+) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 90461f49e9..669dbe5b03 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -682,6 +682,15 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs) retval = PTR_ERR(interpreter); if (IS_ERR(interpreter)) goto out_free_interp; + + /* + * 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 != BINPRM_BUF_SIZE) { diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c index 6e6d4568d5..a4d933a512 100644 --- a/fs/binfmt_elf_fdpic.c +++ b/fs/binfmt_elf_fdpic.c @@ -234,6 +234,14 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm, 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) -- 2.39.5