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| author | Thadeu Lima de Souza Cascardo <cascardo@canonical.com> | 2018-06-07 17:11:01 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-06-07 17:34:39 -0700 |
| commit | 5cc41e099504b77014358b58567c5ea6293dd220 (patch) | |
| tree | 6ed02676effe6f9c55f5a7cb25710ed704aeab7b /fs | |
| parent | 12c253abb9c9d8e01d9365fc8cbde4688731f401 (diff) | |
| download | linux-5cc41e099504b77014358b58567c5ea6293dd220.tar.bz2 | |
fs/binfmt_misc.c: do not allow offset overflow
WHen registering a new binfmt_misc handler, it is possible to overflow
the offset to get a negative value, which might crash the system, or
possibly leak kernel data.
Here is a crash log when 2500000000 was used as an offset:
BUG: unable to handle kernel paging request at ffff989cfd6edca0
IP: load_misc_binary+0x22b/0x470 [binfmt_misc]
PGD 1ef3e067 P4D 1ef3e067 PUD 0
Oops: 0000 [#1] SMP NOPTI
Modules linked in: binfmt_misc kvm_intel ppdev kvm irqbypass joydev input_leds serio_raw mac_hid parport_pc qemu_fw_cfg parpy
CPU: 0 PID: 2499 Comm: bash Not tainted 4.15.0-22-generic #24-Ubuntu
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.1-1 04/01/2014
RIP: 0010:load_misc_binary+0x22b/0x470 [binfmt_misc]
Call Trace:
search_binary_handler+0x97/0x1d0
do_execveat_common.isra.34+0x667/0x810
SyS_execve+0x31/0x40
do_syscall_64+0x73/0x130
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
Use kstrtoint instead of simple_strtoul. It will work as the code
already set the delimiter byte to '\0' and we only do it when the field
is not empty.
Tested with offsets -1, 2500000000, UINT_MAX and INT_MAX. Also tested
with examples documented at Documentation/admin-guide/binfmt-misc.rst
and other registrations from packages on Ubuntu.
Link: http://lkml.kernel.org/r/20180529135648.14254-1-cascardo@canonical.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/binfmt_misc.c | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c index a41b48f82a70..4de191563261 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -387,8 +387,13 @@ static Node *create_entry(const char __user *buffer, size_t count) s = strchr(p, del); if (!s) goto einval; - *s++ = '\0'; - e->offset = simple_strtoul(p, &p, 10); + *s = '\0'; + if (p != s) { + int r = kstrtoint(p, 10, &e->offset); + if (r != 0 || e->offset < 0) + goto einval; + } + p = s; if (*p++) goto einval; pr_debug("register: offset: %#x\n", e->offset); @@ -428,7 +433,8 @@ static Node *create_entry(const char __user *buffer, size_t count) if (e->mask && string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size) goto einval; - if (e->size + e->offset > BINPRM_BUF_SIZE) + if (e->size > BINPRM_BUF_SIZE || + BINPRM_BUF_SIZE - e->size < e->offset) goto einval; pr_debug("register: magic/mask length: %i\n", e->size); if (USE_DEBUG) { |