Date: Sun, 27 Nov 2011 19:36:36 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-8@freebsd.org Subject: svn commit: r228038 - stable/8/sys/kern Message-ID: <201111271936.pARJaakd053389@svn.freebsd.org>
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Author: kib Date: Sun Nov 27 19:36:36 2011 New Revision: 228038 URL: http://svn.freebsd.org/changeset/base/228038 Log: MFC r227485: To limit amount of the kernel memory allocated, and to optimize the iteration over the fdsets, kern_select() limits the length of the fdsets copied in by the last valid file descriptor index. If any bit is set in a mask above the limit, current implementation ignores the filedescriptor, instead of returning EBADF. Fix the issue by scanning the tails of fdset before entering the select loop and returning EBADF if any bit above last valid filedescriptor index is set. The performance impact of the additional check is only imposed on the (somewhat) buggy applications that pass bad file descriptors to select(2) or pselect(2). PR: kern/155606, kern/162379 Modified: stable/8/sys/kern/sys_generic.c Directory Properties: stable/8/sys/ (props changed) Modified: stable/8/sys/kern/sys_generic.c ============================================================================== --- stable/8/sys/kern/sys_generic.c Sun Nov 27 19:13:45 2011 (r228037) +++ stable/8/sys/kern/sys_generic.c Sun Nov 27 19:36:36 2011 (r228038) @@ -829,6 +829,54 @@ select(struct thread *td, struct select_ NFDBITS)); } +/* + * In the unlikely case when user specified n greater then the last + * open file descriptor, check that no bits are set after the last + * valid fd. We must return EBADF if any is set. + * + * There are applications that rely on the behaviour. + * + * nd is fd_lastfile + 1. + */ +static int +select_check_badfd(fd_set *fd_in, int nd, int ndu, int abi_nfdbits) +{ + char *addr, *oaddr; + int b, i, res; + uint8_t bits; + + if (nd >= ndu || fd_in == NULL) + return (0); + + oaddr = NULL; + bits = 0; /* silence gcc */ + for (i = nd; i < ndu; i++) { + b = i / NBBY; +#if BYTE_ORDER == LITTLE_ENDIAN + addr = (char *)fd_in + b; +#else + addr = (char *)fd_in; + if (abi_nfdbits == NFDBITS) { + addr += rounddown(b, sizeof(fd_mask)) + + sizeof(fd_mask) - 1 - b % sizeof(fd_mask); + } else { + addr += rounddown(b, sizeof(uint32_t)) + + sizeof(uint32_t) - 1 - b % sizeof(uint32_t); + } +#endif + if (addr != oaddr) { + res = fubyte(addr); + if (res == -1) + return (EFAULT); + oaddr = addr; + bits = res; + } + if ((bits & (1 << (i % NBBY))) != 0) + return (EBADF); + } + return (0); +} + int kern_select(struct thread *td, int nd, fd_set *fd_in, fd_set *fd_ou, fd_set *fd_ex, struct timeval *tvp, int abi_nfdbits) @@ -843,14 +891,26 @@ kern_select(struct thread *td, int nd, f fd_mask s_selbits[howmany(2048, NFDBITS)]; fd_mask *ibits[3], *obits[3], *selbits, *sbp; struct timeval atv, rtv, ttv; - int error, timo; + int error, lf, ndu, timo; u_int nbufbytes, ncpbytes, ncpubytes, nfdbits; if (nd < 0) return (EINVAL); fdp = td->td_proc->p_fd; - if (nd > fdp->fd_lastfile + 1) - nd = fdp->fd_lastfile + 1; + ndu = nd; + lf = fdp->fd_lastfile; + if (nd > lf + 1) + nd = lf + 1; + + error = select_check_badfd(fd_in, nd, ndu, abi_nfdbits); + if (error != 0) + return (error); + error = select_check_badfd(fd_ou, nd, ndu, abi_nfdbits); + if (error != 0) + return (error); + error = select_check_badfd(fd_ex, nd, ndu, abi_nfdbits); + if (error != 0) + return (error); /* * Allocate just enough bits for the non-null fd_sets. Use the
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