From 96e02d1586782eadf051fa3d6bc4132d2447ac2c Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Sat, 4 Feb 2012 10:47:10 +0100 Subject: 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 Signed-off-by: Heiko Carstens Signed-off-by: Linus Torvalds --- include/linux/binfmts.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/linux/binfmts.h') diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index fd88a39..0092102 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -18,7 +18,7 @@ struct pt_regs; #define BINPRM_BUF_SIZE 128 #ifdef __KERNEL__ -#include +#include #define CORENAME_MAX_SIZE 128 @@ -58,6 +58,7 @@ struct linux_binprm { unsigned interp_flags; unsigned interp_data; unsigned long loader, exec; + char tcomm[TASK_COMM_LEN]; }; #define BINPRM_FLAGS_ENFORCE_NONDUMP_BIT 0 -- cgit v1.1