diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2009-08-01 10:34:56 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2009-09-08 20:17:34 -0700 |
| commit | f43ef685dd388d9b255b5ab15e6f587668bcc7c1 (patch) | |
| tree | 12efcae50553803d308c95d7ed592934425a40fb | |
| parent | bbe5cbd01823805a7cbba06b043c19b559e324c4 (diff) | |
do_sigaltstack: avoid copying 'stack_t' as a structure to user space
commit 0083fc2c50e6c5127c2802ad323adf8143ab7856 upstream.
Ulrich Drepper correctly points out that there is generally padding in
the structure on 64-bit hosts, and that copying the structure from
kernel to user space can leak information from the kernel stack in those
padding bytes.
Avoid the whole issue by just copying the three members one by one
instead, which also means that the function also can avoid the need for
a stack frame. This also happens to match how we copy the new structure
from user space, so it all even makes sense.
[ The obvious solution of adding a memset() generates horrid code, gcc
does really stupid things. ]
Reported-by: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | kernel/signal.c | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index 7d0a222936f5..de2b6494c457 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2353,11 +2353,9 @@ do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long s stack_t oss; int error; - if (uoss) { - oss.ss_sp = (void __user *) current->sas_ss_sp; - oss.ss_size = current->sas_ss_size; - oss.ss_flags = sas_ss_flags(sp); - } + oss.ss_sp = (void __user *) current->sas_ss_sp; + oss.ss_size = current->sas_ss_size; + oss.ss_flags = sas_ss_flags(sp); if (uss) { void __user *ss_sp; @@ -2400,13 +2398,16 @@ do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long s current->sas_ss_size = ss_size; } + error = 0; if (uoss) { error = -EFAULT; - if (copy_to_user(uoss, &oss, sizeof(oss))) + if (!access_ok(VERIFY_WRITE, uoss, sizeof(*uoss))) goto out; + error = __put_user(oss.ss_sp, &uoss->ss_sp) | + __put_user(oss.ss_size, &uoss->ss_size) | + __put_user(oss.ss_flags, &uoss->ss_flags); } - error = 0; out: return error; } |