linux/ipc/msgutil.c, branch v3.12.14

ipc, msg: fix message length check for negative values

2013-12-04T19:05:22Z

commit 4e9b45a19241354daec281d7a785739829b52359 upstream. On 64 bit systems the test for negative message sizes is bogus as the size, which may be positive when evaluated as a long, will get truncated to an int when passed to load_msg(). So a long might very well contain a positive value but when truncated to an int it would become negative. That in combination with a small negative value of msg_ctlmax (which will be promoted to an unsigned type for the comparison against msgsz, making it a big positive value and therefore make it pass the check) will lead to two problems: 1/ The kmalloc() call in alloc_msg() will allocate a too small buffer as the addition of alen is effectively a subtraction. 2/ The copy_from_user() call in load_msg() will first overflow the buffer with userland data and then, when the userland access generates an access violation, the fixup handler copy_user_handle_tail() will try to fill the remainder with zeros -- roughly 4GB. That almost instantly results in a system crash or reset. ,-[ Reproducer (needs to be run as root) ]-- | #include | #include | #include | #include | | int main(void) { | long msg = 1; | int fd; | | fd = open("/proc/sys/kernel/msgmax", O_WRONLY); | write(fd, "-1", 2); | close(fd); | | msgsnd(0, &msg, 0xfffffff0, IPC_NOWAIT); | | return 0; | } '--- Fix the issue by preventing msgsz from getting truncated by consistently using size_t for the message length. This way the size checks in do_msgsnd() could still be passed with a negative value for msg_ctlmax but we would fail on the buffer allocation in that case and error out. Also change the type of m_ts from int to size_t to avoid similar nastiness in other code paths -- it is used in similar constructs, i.e. signed vs. unsigned checks. It should never become negative under normal circumstances, though. Setting msg_ctlmax to a negative value is an odd configuration and should be prevented. As that might break existing userland, it will be handled in a separate commit so it could easily be reverted and reworked without reintroducing the above described bug. Hardening mechanisms for user copy operations would have catched that bug early -- e.g. checking slab object sizes on user copy operations as the usercopy feature of the PaX patch does. Or, for that matter, detect the long vs. int sign change due to truncation, as the size overflow plugin of the very same patch does. [akpm@linux-foundation.org: fix i386 min() warnings] Signed-off-by: Mathias Krause Cc: Pax Team Cc: Davidlohr Bueso Cc: Brad Spengler Cc: Manfred Spraul Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2013-05-02T00:51:54Z

Pull VFS updates from Al Viro, Misc cleanups all over the place, mainly wrt /proc interfaces (switch create_proc_entry to proc_create(), get rid of the deprecated create_proc_read_entry() in favor of using proc_create_data() and seq_file etc). 7kloc removed. * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (204 commits) don't bother with deferred freeing of fdtables proc: Move non-public stuff from linux/proc_fs.h to fs/proc/internal.h proc: Make the PROC_I() and PDE() macros internal to procfs proc: Supply a function to remove a proc entry by PDE take cgroup_open() and cpuset_open() to fs/proc/base.c ppc: Clean up scanlog ppc: Clean up rtas_flash driver somewhat hostap: proc: Use remove_proc_subtree() drm: proc: Use remove_proc_subtree() drm: proc: Use minor->index to label things, not PDE->name drm: Constify drm_proc_list[] zoran: Don't print proc_dir_entry data in debug reiserfs: Don't access the proc_dir_entry in r_open(), r_start() r_show() proc: Supply an accessor for getting the data from a PDE's parent airo: Use remove_proc_subtree() rtl8192u: Don't need to save device proc dir PDE rtl8187se: Use a dir under /proc/net/r8180/ proc: Add proc_mkdir_data() proc: Move some bits from linux/proc_fs.h to linux/{of.h,signal.h,tty.h} proc: Move PDE_NET() to fs/proc/proc_net.c ...

proc: Split the namespace stuff out into linux/proc_ns.h

2013-05-01T21:29:39Z

Split the proc namespace stuff out into linux/proc_ns.h. Signed-off-by: David Howells cc: netdev@vger.kernel.org cc: Serge E. Hallyn cc: Eric W. Biederman Signed-off-by: Al Viro

ipc/msgutil.c: use linux/uaccess.h

2013-05-01T15:12:57Z

Signed-off-by: HoSung Jung Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: set EFAULT as default error in load_msg()

2013-05-01T15:12:57Z

Signed-off-by: Peter Hurley Acked-by: Stanislav Kinsbursky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: tighten msg copy loops

2013-05-01T15:12:57Z

Signed-off-by: Peter Hurley Acked-by: Stanislav Kinsbursky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: separate msg allocation from userspace copy

2013-05-01T15:12:57Z

Separating msg allocation enables single-block vmalloc allocation instead. Signed-off-by: Peter Hurley Acked-by: Stanislav Kinsbursky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: clamp with min()

2013-05-01T15:12:57Z

Signed-off-by: Peter Hurley Acked-by: Stanislav Kinsbursky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: fix potential oops when src msg > 4k w/ MSG_COPY

2013-03-08T23:05:33Z

If the src msg is > 4k, then dest->next points to the next allocated segment; resetting it just prior to dereferencing is bad. Signed-off-by: Peter Hurley Acked-by: Stanislav Kinsbursky Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: simplify message copying

2013-01-05T00:11:46Z

Remove the redundant and confusing fill_copy(). Also add copy_msg() check for error. In this case exit from the function have to be done instead of break, because further code interprets any error as EAGAIN. Also define copy_msg() for the case when CONFIG_CHECKPOINT_RESTORE is disabled. Signed-off-by: Stanislav Kinsbursky Cc: "Eric W. Biederman" Cc: James Morris Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds