Date: Mon, 7 Jun 2021 16:33:04 GMT From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 620a48f64d08 - stable/13 - kern linker: do not allow more than one kldload and kldunload syscalls simultaneously Message-ID: <202106071633.157GX4pR004097@gitrepo.freebsd.org>
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The branch stable/13 has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=620a48f64d0848ce4ef698b3c2aae960a146cc42 commit 620a48f64d0848ce4ef698b3c2aae960a146cc42 Author: Konstantin Belousov <kib@FreeBSD.org> AuthorDate: 2021-05-20 14:50:43 +0000 Commit: Konstantin Belousov <kib@FreeBSD.org> CommitDate: 2021-06-07 16:32:42 +0000 kern linker: do not allow more than one kldload and kldunload syscalls simultaneously (cherry picked from commit e266a0f7f001c7886eab56d8c058d92d87010400) --- sys/kern/kern_linker.c | 86 +++++++++++++++++++++++++++++++++++++++----------- sys/sys/linker.h | 9 ++++++ 2 files changed, 77 insertions(+), 18 deletions(-) diff --git a/sys/kern/kern_linker.c b/sys/kern/kern_linker.c index e54546eec7b4..dbbf240a2f56 100644 --- a/sys/kern/kern_linker.c +++ b/sys/kern/kern_linker.c @@ -106,6 +106,7 @@ MALLOC_DEFINE(M_LINKER, "linker", "kernel linker"); linker_file_t linker_kernel_file; static struct sx kld_sx; /* kernel linker lock */ +static bool kld_busy; /* * Load counter used by clients to determine if a linker file has been @@ -1050,6 +1051,49 @@ linker_search_symbol_name(caddr_t value, char *buf, u_int buflen, M_WAITOK)); } +int +linker_kldload_busy(int flags) +{ + int error; + + MPASS((flags & ~(LINKER_UB_UNLOCK | LINKER_UB_LOCKED | + LINKER_UB_PCATCH)) == 0); + if ((flags & LINKER_UB_LOCKED) != 0) + sx_assert(&kld_sx, SA_XLOCKED); + + if ((flags & LINKER_UB_LOCKED) == 0) + sx_xlock(&kld_sx); + while (kld_busy) { + error = sx_sleep(&kld_busy, &kld_sx, + (flags & LINKER_UB_PCATCH) != 0 ? PCATCH : 0, + "kldbusy", 0); + if (error != 0) { + if ((flags & LINKER_UB_UNLOCK) != 0) + sx_xunlock(&kld_sx); + return (error); + } + } + kld_busy = true; + if ((flags & LINKER_UB_UNLOCK) != 0) + sx_xunlock(&kld_sx); + return (0); +} + +void +linker_kldload_unbusy(int flags) +{ + MPASS((flags & ~LINKER_UB_LOCKED) == 0); + if ((flags & LINKER_UB_LOCKED) != 0) + sx_assert(&kld_sx, SA_XLOCKED); + + if ((flags & LINKER_UB_LOCKED) == 0) + sx_xlock(&kld_sx); + MPASS(kld_busy); + kld_busy = false; + wakeup(&kld_busy); + sx_xunlock(&kld_sx); +} + /* * Syscalls. */ @@ -1066,12 +1110,6 @@ kern_kldload(struct thread *td, const char *file, int *fileid) if ((error = priv_check(td, PRIV_KLD_LOAD)) != 0) return (error); - /* - * It is possible that kldloaded module will attach a new ifnet, - * so vnet context must be set when this ocurs. - */ - CURVNET_SET(TD_TO_VNET(td)); - /* * If file does not contain a qualified name or any dot in it * (kldname.ko, or kldname.ver.ko) treat it as an interface @@ -1085,19 +1123,27 @@ kern_kldload(struct thread *td, const char *file, int *fileid) modname = file; } - sx_xlock(&kld_sx); - error = linker_load_module(kldname, modname, NULL, NULL, &lf); - if (error) { + error = linker_kldload_busy(LINKER_UB_PCATCH); + if (error != 0) { sx_xunlock(&kld_sx); - goto done; + return (error); } - lf->userrefs++; - if (fileid != NULL) - *fileid = lf->id; - sx_xunlock(&kld_sx); -done: + /* + * It is possible that kldloaded module will attach a new ifnet, + * so vnet context must be set when this ocurs. + */ + CURVNET_SET(TD_TO_VNET(td)); + + error = linker_load_module(kldname, modname, NULL, NULL, &lf); CURVNET_RESTORE(); + + if (error == 0) { + lf->userrefs++; + if (fileid != NULL) + *fileid = lf->id; + } + linker_kldload_unbusy(LINKER_UB_LOCKED); return (error); } @@ -1132,8 +1178,13 @@ kern_kldunload(struct thread *td, int fileid, int flags) if ((error = priv_check(td, PRIV_KLD_UNLOAD)) != 0) return (error); + error = linker_kldload_busy(LINKER_UB_PCATCH); + if (error != 0) { + sx_xunlock(&kld_sx); + return (error); + } + CURVNET_SET(TD_TO_VNET(td)); - sx_xlock(&kld_sx); lf = linker_find_file_by_id(fileid); if (lf) { KLD_DPF(FILE, ("kldunload: lf->userrefs=%d\n", lf->userrefs)); @@ -1153,9 +1204,8 @@ kern_kldunload(struct thread *td, int fileid, int flags) } } else error = ENOENT; - sx_xunlock(&kld_sx); - CURVNET_RESTORE(); + linker_kldload_unbusy(LINKER_UB_LOCKED); return (error); } diff --git a/sys/sys/linker.h b/sys/sys/linker.h index 13274ecd1a7c..6423a3989a02 100644 --- a/sys/sys/linker.h +++ b/sys/sys/linker.h @@ -196,6 +196,15 @@ int linker_search_symbol_name(caddr_t value, char *buf, u_int buflen, /* HWPMC helper */ void *linker_hwpmc_list_objects(void); +/* kldload/kldunload syscalls blocking */ +#define LINKER_UB_UNLOCK 0x0001 /* busy: unlock kld_sx locked on + return */ +#define LINKER_UB_LOCKED 0x0002 /* busy/unbusy: kld_sx locked on + entry */ +#define LINKER_UB_PCATCH 0x0004 /* busy: sleep interruptible */ +int linker_kldload_busy(int flags); +void linker_kldload_unbusy(int flags); + #endif /* _KERNEL */ /*
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