svn commit: r212723 - head/sys/compat/linprocfs
Kostik Belousov
kostikbel at gmail.com
Fri Sep 24 13:32:20 UTC 2010
On Fri, Sep 24, 2010 at 08:34:16AM -0400, John Baldwin wrote:
> On Friday, September 24, 2010 7:53:11 am Kostik Belousov wrote:
> > On Fri, Sep 24, 2010 at 02:17:29PM +0400, pluknet wrote:
> > > On 16 September 2010 11:56, Dag-Erling Smorgrav <des at freebsd.org> wrote:
> > > > Author: des
> > > > Date: Thu Sep 16 07:56:34 2010
> > > > New Revision: 212723
> > > > URL: http://svn.freebsd.org/changeset/base/212723
> > > >
> > > > Log:
> > > > Implement proc/$$/environment.
> > > >
> > > [...]
> > >
> > > > /*
> > > > * Filler function for proc/pid/environ
> > > > */
> > > > static int
> > > > linprocfs_doprocenviron(PFS_FILL_ARGS)
> > > > {
> > > > + int ret;
> > > >
> > > > - sbuf_printf(sb, "doprocenviron\n%c", '\0');
> > > > - return (0);
> > > > + PROC_LOCK(p);
> > >
> > > With this change I observe the following sleepable after non-sleepable:
> > >
> > > 1st 0xffffff000290b558 process lock (process lock) @
> > > /usr/src/sys/modules/linprocfs/../../compat/linprocfs/linprocfs.c:1049
> > > 2nd 0xffffff00028f8848 user map (user map) @
> /usr/src/sys/vm/vm_map.c:3525
> > > KDB: stack backtrace:
> > > db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
> > > _witness_debugger() at _witness_debugger+0x2e
> > > witness_checkorder() at witness_checkorder+0x807
> > > _sx_slock() at _sx_slock+0x55
> > > vm_map_lookup() at vm_map_lookup+0x55
> > > vm_fault() at vm_fault+0x113
> > > proc_rwmem() at proc_rwmem+0x7a
> > > linprocfs_doprocenviron() at linprocfs_doprocenviron+0x122
> > > pfs_read() at pfs_read+0x45b
> > > vn_read() at vn_read+0x256
> > > dofileread() at dofileread+0xa1
> > > kern_readv() at kern_readv+0x60
> > > read() at read+0x55
> > > syscallenter() at syscallenter+0x1aa
> > > syscall() at syscall+0x4c
> > > Xfast_syscall() at Xfast_syscall+0xe2
> > > --- syscall (3, FreeBSD ELF64, read), rip = 0x80074134c, rsp =
> > > 0x7fffffffe9c8, rbp = 0 ---
> > >
> > >
> > > > +
> > > > + if ((ret = p_cansee(td, p)) != 0) {
> > > > + PROC_UNLOCK(p);
> > > > + return ret;
> > > > + }
> > > > +
> > > > + ret = linprocfs_doargv(td, p, sb, ps_string_env);
> > > > + PROC_UNLOCK(p);
> > > > + return (ret);
> > > > }
> >
> > This is easy to fix, isn't it ? But there seems to be much more nits.
> >
> > First, allocating 512 * sizeof(char *)-byte object on the stack is not
> > good.
> >
> > Second, the initialization of iov_len for reading the array
> > of string pointers misses '* sizeof(char *)'.
> >
> > And third (probably fatal) is the lack of checks that the end of
> > array and each string fits into the user portion of the map. I do not
> > see why addr that already has u_long type is casted to u_long. Also,
> > VM_MIN_ADDRESS, VM_MAXUSER_ADDRESS constants are for the native host
> > FreeBSD ABI, they may differ from the target process limits.
> >
> > Formatting is separate issue, let postpone it.
> >
> > diff --git a/sys/compat/linprocfs/linprocfs.c
> b/sys/compat/linprocfs/linprocfs.c
> > index c7fe158..fd62b1c 100644
> > --- a/sys/compat/linprocfs/linprocfs.c
> > +++ b/sys/compat/linprocfs/linprocfs.c
> > @@ -952,12 +952,9 @@ linprocfs_doargv(struct thread *td, struct proc *p,
> struct sbuf *sb,
> > struct uio tmp_uio;
> > struct ps_strings pss;
> > int ret, i, n_elements, found_end;
> > - u_long addr;
> > - char* env_vector[MAX_ARGV_STR];
> > + u_long addr, pbegin;
> > + char **env_vector;
> > char env_string[UIO_CHUNK_SZ];
> > - char *pbegin;
> > -
> > -
> >
> > #define UIO_HELPER(uio, iov, base, len, cnt, offset, sz, flg, rw, td) \
> > do { \
> > @@ -971,6 +968,10 @@ do { \
> > uio.uio_rw = (rw); \
> > uio.uio_td = (td); \
> > } while (0)
> > +#define VALID_USER_ADDR(addr) \
> > + ((addr) >= p->p_sysent->sv_minuser && (addr) < p->p_sysent->sv_maxuser)
> > +
> > + env_vector = malloc(sizeof(char *) * MAX_ARGV_STR, M_TEMP, M_WAITOK);
> >
> > UIO_HELPER(tmp_uio, iov, &pss, sizeof(struct ps_strings), 1,
> > (off_t)(p->p_sysent->sv_psstrings), sizeof(struct ps_strings),
> > @@ -978,37 +979,41 @@ do { \
> >
> > ret = proc_rwmem(p, &tmp_uio);
> > if (ret != 0)
> > - return ret;
> > + goto done;
> >
> > /* Get the array address and the number of elements */
> > resolver(pss, &addr, &n_elements);
> >
> > /* Consistent with lib/libkvm/kvm_proc.c */
> > - if (n_elements > MAX_ARGV_STR || (u_long)addr < VM_MIN_ADDRESS ||
> > - (u_long)addr >= VM_MAXUSER_ADDRESS) {
> > - /* What error code should we return? */
> > - return 0;
> > + if (n_elements > MAX_ARGV_STR || !VALID_USER_ADDR(addr) ||
> > + !VALID_USER_ADDR(addr + MAX_ARGV_STR * sizeof(char *))) {
> > + ret = EFAULT;
> > + goto done;
> > }
> >
> > - UIO_HELPER(tmp_uio, iov, env_vector, MAX_ARGV_STR, 1,
> > + UIO_HELPER(tmp_uio, iov, env_vector, MAX_ARGV_STR * sizeof(char *), 1,
> > (vm_offset_t)(addr), iov.iov_len, UIO_SYSSPACE, UIO_READ, td);
> >
> > ret = proc_rwmem(p, &tmp_uio);
> > if (ret != 0)
> > - return ret;
> > + goto done;
> >
> > /* Now we can iterate through the list of strings */
> > for (i = 0; i < n_elements; i++) {
> > found_end = 0;
> > - pbegin = env_vector[i];
> > - while(!found_end) {
> > + pbegin = (vm_offset_t)env_vector[i];
> > + while (!found_end) {
> > + if (!VALID_USER_ADDR(pbegin) ||
> > + !VALID_USER_ADDR(pbegin + sizeof(env_string))) {
> > + ret = EFAULT;
> > + goto done;
> > + }
> > UIO_HELPER(tmp_uio, iov, env_string, sizeof(env_string), 1,
> > - (vm_offset_t) pbegin, iov.iov_len, UIO_SYSSPACE,
> > - UIO_READ, td);
> > + pbegin, iov.iov_len, UIO_SYSSPACE, UIO_READ, td);
> >
> > ret = proc_rwmem(p, &tmp_uio);
> > if (ret != 0)
> > - return ret;
> > + goto done;
> >
> > if (!strvalid(env_string, UIO_CHUNK_SZ)) {
> > /*
> > @@ -1017,7 +1022,7 @@ do { \
> > * the pointer
> > */
> > sbuf_bcat(sb, env_string, UIO_CHUNK_SZ);
> > - pbegin = &(*pbegin) + UIO_CHUNK_SZ;
> > + pbegin += UIO_CHUNK_SZ;
> > } else {
> > found_end = 1;
> > }
> > @@ -1025,9 +1030,12 @@ do { \
> > sbuf_printf(sb, "%s", env_string);
> > }
> >
> > +#undef VALID_USER_ADDR
> > #undef UIO_HELPER
> >
> > - return (0);
> > +done:
> > + free(env_vector, M_TEMP);
> > + return (ret);
> > }
> >
> > static void
> > @@ -1052,9 +1060,11 @@ linprocfs_doprocenviron(PFS_FILL_ARGS)
> > PROC_UNLOCK(p);
> > return ret;
> > }
> > + _PHOLD(p);
> > + PROC_UNLOCK(p);
> >
> > ret = linprocfs_doargv(td, p, sb, ps_string_env);
> > - PROC_UNLOCK(p);
> > + PRELE(p);
> > return (ret);
> > }
>
> You need to add a P_WEXIT check here. _PHOLD() / PRELE() do not work
> once P_WEXIT is set (rather, exit1() may not notice and wait for a
> _PHOLD() invoked to drain once P_WEXIT is set).
Hmm, I think that PHOLD is not needed there, actually. Pseudofs
checks for exiting process in pfs_visible(_proc). Before the fill
method is called, process is held and unlocked. So my second _PHOLD
could be removed.
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