Subject: + fs-binfmts-better-handling-of-binfmt-loops.patch added to -mm tree To: zml@xxxxxxxxxxxxxxxxxx,viro@xxxxxxxxxxxxxxxxxx,zach@xxxxxxxxxxxxxxx From: akpm@xxxxxxxxxxxxxxxxxxxx Date: Tue, 30 Jul 2013 14:06:38 -0700 The patch titled Subject: fs/binfmts: better handling of binfmt loops has been added to the -mm tree. Its filename is fs-binfmts-better-handling-of-binfmt-loops.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/fs-binfmts-better-handling-of-binfmt-loops.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/fs-binfmts-better-handling-of-binfmt-loops.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Zach Levis <zml@xxxxxxxxxxxxxxxxxx> Subject: fs/binfmts: better handling of binfmt loops With these changes, when a binfmt loop is encountered, the ELOOP will propagate back to the 0 depth. At this point the argv and argc values will be reset to what they were originally and an attempt is made to continue with the following binfmt handlers. Caveats: - binfmt_misc is skipped as a whole. To allow for a more generic solution that works for any binfmt without a lot of duplicated code and added complexity, the error detection code is applied on the binfmt level. - This is a fallback solution. It attempts to restore the state to allow executing most binaries without side effects, but it may not work for everything and should not be depended on for regular usage. My (rough, but functional) test scripts for this issue are available at: https://gist.github.com/zml2008/6075418 Signed-off-by: Zach Levis <zach@xxxxxxxxxxxxxxx> Signed-off-by: Zach Levis <zml@xxxxxxxxxxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/exec.c | 30 +++++++++++++++++++++++++++++- include/linux/binfmts.h | 5 ++++- 2 files changed, 33 insertions(+), 2 deletions(-) diff -puN fs/exec.c~fs-binfmts-better-handling-of-binfmt-loops fs/exec.c --- a/fs/exec.c~fs-binfmts-better-handling-of-binfmt-loops +++ a/fs/exec.c @@ -1403,13 +1403,40 @@ int search_binary_handler(struct linux_b if (!try_module_get(fmt->module)) continue; read_unlock(&binfmt_lock); + bprm->previous_binfmts[1] = bprm->previous_binfmts[0]; + bprm->previous_binfmts[0] = fmt; + bprm->recursion_depth = depth + 1; retval = fn(bprm); bprm->recursion_depth = depth; + if (retval == -ELOOP && depth == 0) { /* cur, previous */ + pr_err("Too much recursion with binfmts (0:%s, -1:%s) in file %s, skipping (base %s).\n", + bprm->previous_binfmts[0]->name, + bprm->previous_binfmts[1]->name, + bprm->filename, + fmt->name); + + /* Put argv back in its place */ + while (bprm->argc > 0) { + retval = remove_arg_zero(bprm); + if (retval) + return retval; + } + + copy_strings(bprm->argc_orig, *((struct user_arg_ptr *) bprm->argv_orig), bprm); + bprm->argc = bprm->argc_orig; + retval = -ENOEXEC; + continue; + } + if (retval >= 0) { if (depth == 0) { trace_sched_process_exec(current, old_pid, bprm); ptrace_event(PTRACE_EVENT_EXEC, old_vpid); + /* Successful execution, now null out the cached argv + * (we don't want to access it later) + * */ + bprm->argv_orig = NULL; } put_binfmt(fmt); allow_write_access(bprm->file); @@ -1516,7 +1543,7 @@ static int do_execve_common(const char * if (retval) goto out_file; - bprm->argc = count(argv, MAX_ARG_STRINGS); + bprm->argc_orig = bprm->argc = count(argv, MAX_ARG_STRINGS); if ((retval = bprm->argc) < 0) goto out; @@ -1540,6 +1567,7 @@ static int do_execve_common(const char * retval = copy_strings(bprm->argc, argv, bprm); if (retval < 0) goto out; + bprm->argv_orig = &argv; retval = search_binary_handler(bprm); if (retval < 0) diff -puN include/linux/binfmts.h~fs-binfmts-better-handling-of-binfmt-loops include/linux/binfmts.h --- a/include/linux/binfmts.h~fs-binfmts-better-handling-of-binfmt-loops +++ a/include/linux/binfmts.h @@ -32,11 +32,14 @@ struct linux_binprm { unsigned int taso:1; #endif unsigned int recursion_depth; + /* current binfmt at 0 and previous binfmt at 1 */ + struct linux_binfmt *previous_binfmts[2]; struct file * file; struct cred *cred; /* new credentials */ int unsafe; /* how unsafe this exec is (mask of LSM_UNSAFE_*) */ unsigned int per_clear; /* bits to clear in current->personality */ - int argc, envc; + int argc, argc_orig, envc; + void *argv_orig; const char * filename; /* Name of binary as seen by procps */ const char * interp; /* Name of the binary really executed. Most of the time same as filename, but could be _ Patches currently in -mm which might be from zml@xxxxxxxxxxxxxxxxxx are fs-binfmts-add-a-name-field-to-the-binfmt-struct.patch fs-binfmts-better-handling-of-binfmt-loops.patch fs-binfmts-whitespace-fixes-with-scripts-cleanfile.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html