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author | Helge Deller <deller@gmx.de> | 2015-06-04 23:57:18 +0200 |
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committer | Helge Deller <deller@gmx.de> | 2015-06-04 23:57:18 +0200 |
commit | 9b7b819ca1e508195feed5ece558dca66adeef05 (patch) | |
tree | cf62f858c89c61d5b38052273ff7ca2defb3a818 /kernel/compat.c | |
parent | ff25ea8f4eeea252bfcaf65289fa57ba6de080dd (diff) | |
download | linux-9b7b819ca1e508195feed5ece558dca66adeef05.tar.gz |
compat: cleanup coding in compat_get_bitmap() and compat_put_bitmap()
In the functions compat_get_bitmap() and compat_put_bitmap() the variable nr_compat_longs stores how many compat_ulong_t words should be copied in a loop. The copy loop itself is this: if (nr_compat_longs-- > 0) { if (__get_user(um, umask)) return -EFAULT; } else { um = 0; } Since nr_compat_longs gets unconditionally decremented in each loop and since it's type is unsigned this could theoretically lead to out of bounds accesses to userspace if nr_compat_longs wraps around to (unsigned)(-1). Although the callers currently do not trigger out-of-bounds accesses, we should better implement the loop in a safe way to completely avoid such warp-arounds. Signed-off-by: Helge Deller <deller@gmx.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'kernel/compat.c')
-rw-r--r-- | kernel/compat.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/compat.c b/kernel/compat.c index 24f00610c575..333d364be29d 100644 --- a/kernel/compat.c +++ b/kernel/compat.c @@ -912,7 +912,8 @@ long compat_get_bitmap(unsigned long *mask, const compat_ulong_t __user *umask, * bitmap. We must however ensure the end of the * kernel bitmap is zeroed. */ - if (nr_compat_longs-- > 0) { + if (nr_compat_longs) { + nr_compat_longs--; if (__get_user(um, umask)) return -EFAULT; } else { @@ -954,7 +955,8 @@ long compat_put_bitmap(compat_ulong_t __user *umask, unsigned long *mask, * We dont want to write past the end of the userspace * bitmap. */ - if (nr_compat_longs-- > 0) { + if (nr_compat_longs) { + nr_compat_longs--; if (__put_user(um, umask)) return -EFAULT; } |