When the coredump server raises COREDUMP_HEADER every write to the socket is prefixed with a struct coredump_frame_header in front of it describing what follows. A header and the bytes it describes go out in one iovec.
Both emitters write through one helper that either writes the whole iov_iter or fails. So a single place advances the file position. cprm->pos stays the offset in the coredump and keeps ignoring the framing overhead. dump_skip_to() and dump_align() compute from it. cprm->written counts what was handed to the file and so picks the headers up. The two are the same number when the coredump isn't framed. A hole is flushed through __dump_emit() like before. So zeroes still are sent on the socket as actual data frames. Making holes cheap is COREDUMP_SPARSE's job. Signed-off-by: Christian Brauner (Amutable) <[email protected]> --- fs/coredump.c | 114 ++++++++++++++++----- include/linux/coredump.h | 5 + .../selftests/coredump/coredump_test_helpers.c | 2 +- 3 files changed, 94 insertions(+), 27 deletions(-) diff --git a/fs/coredump.c b/fs/coredump.c index 6de18bc49925..364c89c5f82a 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -51,7 +51,6 @@ #include <net/sock.h> #include <uapi/linux/pidfd.h> #include <uapi/linux/un.h> -#include <uapi/linux/coredump.h> #include <linux/uaccess.h> #include <asm/mmu_context.h> @@ -753,6 +752,7 @@ static inline bool coredump_sock_send(struct file *file, struct coredump_req *re static_assert(sizeof(struct coredump_req) == COREDUMP_REQ_SIZE_VER0); static_assert(sizeof(struct coredump_ack) == COREDUMP_ACK_SIZE_VER0); +static_assert(sizeof(struct coredump_frame_header) == COREDUMP_FRAME_HEADER_SIZE_VER0); static_assert(sizeof(enum coredump_mark) == sizeof(__u32)); static inline bool coredump_sock_mark(struct file *file, enum coredump_mark mark) @@ -798,7 +798,8 @@ static bool coredump_sock_request(struct core_name *cn, struct coredump_params * struct coredump_req req = { .size = sizeof(struct coredump_req), .mask = COREDUMP_KERNEL | COREDUMP_USERSPACE | - COREDUMP_REJECT | COREDUMP_WAIT, + COREDUMP_REJECT | COREDUMP_WAIT | + COREDUMP_HEADER, .size_ack = sizeof(struct coredump_ack), }; struct coredump_ack ack = {}; @@ -847,11 +848,24 @@ static bool coredump_sock_request(struct core_name *cn, struct coredump_params * return false; } + /* Framing only applies to a coredump the kernel writes. */ + if ((ack.mask & COREDUMP_HEADER) && !(ack.mask & COREDUMP_KERNEL)) { + coredump_sock_mark(cprm->file, COREDUMP_MARK_CONFLICTING); + return false; + } + if (ack.spare) { coredump_sock_mark(cprm->file, COREDUMP_MARK_UNSUPPORTED); return false; } + /* Frame header scratch; a bvec can't point at the stack. */ + if (ack.mask & COREDUMP_HEADER) { + cprm->frame = kmalloc_obj(*cprm->frame); + if (!cprm->frame) + return false; + } + cprm->mask = ack.mask; return coredump_sock_mark(cprm->file, COREDUMP_MARK_REQACK); } @@ -1053,9 +1067,10 @@ static bool coredump_write(struct core_name *cn, cn->core_dumped = binfmt->core_dump(cprm); /* * Ensures that file size is big enough to contain the current - * file postion. This prevents gdb from complaining about + * file position. This prevents gdb from complaining about * a truncated file if the last "write" to the file was - * dump_skip. + * dump_skip. A framed coredump relies on it too: the flush + * emits the frames that cover a trailing hole. */ if (cprm->to_skip) { cprm->to_skip--; @@ -1075,6 +1090,7 @@ static void coredump_cleanup(struct core_name *cn, struct coredump_params *cprm) atomic_dec(&core_pipe_count); } kfree(cn->corename); + kfree(cprm->frame); coredump_finish(cn->core_dumped); } @@ -1208,24 +1224,72 @@ void vfs_coredump(const kernel_siginfo_t *siginfo) * do on a core-file: use only these functions to write out all the * necessary info. */ -static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr) +static bool dump_framed(const struct coredump_params *cprm) +{ + return cprm->mask & COREDUMP_HEADER; +} + +/* Describe the next @len bytes of the coredump. Returns the header size. */ +static size_t dump_frame_init(struct coredump_params *cprm, + enum coredump_frame_type type, u64 len) +{ + if (!dump_framed(cprm)) + return 0; + + *cprm->frame = (struct coredump_frame_header) { + .size = sizeof(*cprm->frame), + .type = type, + .offset = cprm->pos, + .len = len, + }; + + return sizeof(*cprm->frame); +} + +/* Write @iter whole or fail. @len is what it advances the coredump by. */ +static bool dump_write_iter(struct coredump_params *cprm, struct iov_iter *iter, + size_t len) { struct file *file = cprm->file; + size_t count = iov_iter_count(iter); loff_t pos = file->f_pos; ssize_t n; + n = __kernel_write_iter(file, iter, &pos); + if (n < 0 || (size_t)n != count) + return false; + file->f_pos = pos; + cprm->written += count; + cprm->pos += len; + + return true; +} + +static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr) +{ + struct kvec kvec[2]; + struct iov_iter iter; + unsigned int nseg = 0; + size_t hdr; + if (cprm->written + nr > cprm->limit) return 0; if (dump_interrupted()) return 0; - n = __kernel_write(file, addr, nr, &pos); - if (n != nr) - return 0; - file->f_pos = pos; - cprm->written += n; - cprm->pos += n; - return 1; + hdr = dump_frame_init(cprm, COREDUMP_FRAME_DATA, nr); + if (hdr) { + kvec[nseg].iov_base = cprm->frame; + kvec[nseg].iov_len = hdr; + nseg++; + } + kvec[nseg].iov_base = (void *)addr; + kvec[nseg].iov_len = nr; + nseg++; + + iov_iter_kvec(&iter, ITER_SOURCE, kvec, nseg, hdr + nr); + + return dump_write_iter(cprm, &iter, nr); } static int __dump_skip(struct coredump_params *cprm, size_t nr) @@ -1283,11 +1347,10 @@ EXPORT_SYMBOL(dump_skip); #ifdef CONFIG_ELF_CORE static int dump_emit_page(struct coredump_params *cprm, struct page *page) { - struct bio_vec bvec; + struct bio_vec bvec[2]; struct iov_iter iter; - struct file *file = cprm->file; - loff_t pos; - ssize_t n; + unsigned int nseg = 0; + size_t hdr; if (!page) return 0; @@ -1298,17 +1361,16 @@ static int dump_emit_page(struct coredump_params *cprm, struct page *page) return 0; if (dump_interrupted()) return 0; - pos = file->f_pos; - bvec_set_page(&bvec, page, PAGE_SIZE, 0); - iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE); - n = __kernel_write_iter(cprm->file, &iter, &pos); - if (n != PAGE_SIZE) - return 0; - file->f_pos = pos; - cprm->written += PAGE_SIZE; - cprm->pos += PAGE_SIZE; - return 1; + /* Hand the frame to the same write as the page it describes. */ + hdr = dump_frame_init(cprm, COREDUMP_FRAME_DATA, PAGE_SIZE); + if (hdr) + bvec_set_virt(&bvec[nseg++], cprm->frame, hdr); + bvec_set_page(&bvec[nseg++], page, PAGE_SIZE, 0); + + iov_iter_bvec(&iter, ITER_SOURCE, bvec, nseg, hdr + PAGE_SIZE); + + return dump_write_iter(cprm, &iter, PAGE_SIZE); } /* diff --git a/include/linux/coredump.h b/include/linux/coredump.h index dc7a05b1bb0a..06ccd3046a06 100644 --- a/include/linux/coredump.h +++ b/include/linux/coredump.h @@ -6,6 +6,7 @@ #include <linux/mm.h> #include <linux/fs.h> #include <linux/sched/coredump.h> +#include <uapi/linux/coredump.h> #include <asm/siginfo.h> #ifdef CONFIG_COREDUMP @@ -28,7 +29,11 @@ struct coredump_params { int cpu; /* COREDUMP_* options negotiated with the coredump server. */ u64 mask; + /* Frame header scratch, NULL unless the coredump is framed. */ + struct coredump_frame_header *frame; + /* Bytes handed to the file, frame headers included. */ loff_t written; + /* Offset in the coredump, frame headers excluded. */ loff_t pos; loff_t to_skip; int vma_count; diff --git a/tools/testing/selftests/coredump/coredump_test_helpers.c b/tools/testing/selftests/coredump/coredump_test_helpers.c index d32d96436779..bfe10bc51618 100644 --- a/tools/testing/selftests/coredump/coredump_test_helpers.c +++ b/tools/testing/selftests/coredump/coredump_test_helpers.c @@ -290,7 +290,7 @@ bool send_coredump_ack(int fd, const struct coredump_req *req, /* Every option the kernel is expected to advertise in coredump_req->mask. */ #define COREDUMP_REQ_MASK_ALL \ (COREDUMP_KERNEL | COREDUMP_USERSPACE | \ - COREDUMP_REJECT | COREDUMP_WAIT) + COREDUMP_REJECT | COREDUMP_WAIT | COREDUMP_HEADER) bool check_coredump_req(const struct coredump_req *req) { -- 2.53.0
