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In bpf_setf(), protect against races between multiple user threads

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attempting to change the BPF filter on a BPF descriptor at the same
time: retrieve the old filter pointer under the same locked region
as setting the new pointer.

MFC after:	3 days
This commit is contained in:
rwatson 2005-02-28 14:04:09 +00:00
parent ba21b23c12
commit 6ae9352b09
1 changed files with 2 additions and 1 deletions
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3
sys/net/bpf.c
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@ -947,11 +947,11 @@ bpf_setf(d, fp)
struct bpf_insn *fcode, *old;
u_int flen, size;
old = d->bd_filter;
if (fp->bf_insns == NULL) {
if (fp->bf_len != 0)
return (EINVAL);
BPFD_LOCK(d);
old = d->bd_filter;
d->bd_filter = NULL;
reset_d(d);
BPFD_UNLOCK(d);
@ -968,6 +968,7 @@ bpf_setf(d, fp)
if (copyin((caddr_t)fp->bf_insns, (caddr_t)fcode, size) == 0 &&
bpf_validate(fcode, (int)flen)) {
BPFD_LOCK(d);
old = d->bd_filter;
d->bd_filter = fcode;
reset_d(d);
BPFD_UNLOCK(d);