diff options
| author | Heiko Carstens <heiko.carstens@de.ibm.com> | 2012-02-04 10:47:10 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-02-06 15:15:20 -0800 |
| commit | 96e02d1586782eadf051fa3d6bc4132d2447ac2c (patch) | |
| tree | dd40e6302d2770d3c51cced64cfd3b8cf1355da4 /fs | |
| parent | 23783f817bceedd6d4e549385e3f400ea64059e5 (diff) | |
exec: fix use-after-free bug in setup_new_exec()
Setting the task name is done within setup_new_exec() by accessing
bprm->filename. However this happens after flush_old_exec().
This may result in a use after free bug, flush_old_exec() may
"complete" vfork_done, which will wake up the parent which in turn
may free the passed in filename.
To fix this add a new tcomm field in struct linux_binprm which
contains the now early generated task name until it is used.
Fixes this bug on s390:
Unable to handle kernel pointer dereference at virtual kernel address 0000000039768000
Process kworker/u:3 (pid: 245, task: 000000003a3dc840, ksp: 0000000039453818)
Krnl PSW : 0704000180000000 0000000000282e94 (setup_new_exec+0xa0/0x374)
Call Trace:
([<0000000000282e2c>] setup_new_exec+0x38/0x374)
[<00000000002dd12e>] load_elf_binary+0x402/0x1bf4
[<0000000000280a42>] search_binary_handler+0x38e/0x5bc
[<0000000000282b6c>] do_execve_common+0x410/0x514
[<0000000000282cb6>] do_execve+0x46/0x58
[<00000000005bce58>] kernel_execve+0x28/0x70
[<000000000014ba2e>] ____call_usermodehelper+0x102/0x140
[<00000000005bc8da>] kernel_thread_starter+0x6/0xc
[<00000000005bc8d4>] kernel_thread_starter+0x0/0xc
Last Breaking-Event-Address:
[<00000000002830f0>] setup_new_exec+0x2fc/0x374
Kernel panic - not syncing: Fatal exception: panic_on_oops
Reported-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/exec.c | 33 |
1 files changed, 17 insertions, 16 deletions
diff --git a/fs/exec.c b/fs/exec.c index aeb135c7ff5..92ce83a11e9 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1071,6 +1071,21 @@ void set_task_comm(struct task_struct *tsk, char *buf) perf_event_comm(tsk); } +static void filename_to_taskname(char *tcomm, const char *fn, unsigned int len) +{ + int i, ch; + + /* Copies the binary name from after last slash */ + for (i = 0; (ch = *(fn++)) != '\0';) { + if (ch == '/') + i = 0; /* overwrite what we wrote */ + else + if (i < len - 1) + tcomm[i++] = ch; + } + tcomm[i] = '\0'; +} + int flush_old_exec(struct linux_binprm * bprm) { int retval; @@ -1085,6 +1100,7 @@ int flush_old_exec(struct linux_binprm * bprm) set_mm_exe_file(bprm->mm, bprm->file); + filename_to_taskname(bprm->tcomm, bprm->filename, sizeof(bprm->tcomm)); /* * Release all of the old mmap stuff */ @@ -1116,10 +1132,6 @@ EXPORT_SYMBOL(would_dump); void setup_new_exec(struct linux_binprm * bprm) { - int i, ch; - const char *name; - char tcomm[sizeof(current->comm)]; - arch_pick_mmap_layout(current->mm); /* This is the point of no return */ @@ -1130,18 +1142,7 @@ void setup_new_exec(struct linux_binprm * bprm) else set_dumpable(current->mm, suid_dumpable); - name = bprm->filename; - - /* Copies the binary name from after last slash */ - for (i=0; (ch = *(name++)) != '\0';) { - if (ch == '/') - i = 0; /* overwrite what we wrote */ - else - if (i < (sizeof(tcomm) - 1)) - tcomm[i++] = ch; - } - tcomm[i] = '\0'; - set_task_comm(current, tcomm); + set_task_comm(current, bprm->tcomm); /* Set the new mm task size. We have to do that late because it may * depend on TIF_32BIT which is only updated in flush_thread() on |