Hi Lianbo,
Thanks for the patch, I have run the test and no regressions found. So ack.
Thanks,
Tao Liu
On Fri, Aug 16, 2024 at 2:30 PM Lianbo Jiang <lijiang@xxxxxxxxxx> wrote:
>
> Sometimes, in a production environment, there are still some vmcores
> that are incomplete, such as partial header or the data is corrupted.
> When crash tool attempts to parse such vmcores, it may fail as below:
>
> $ ./crash --osrelease vmcore
> Bus error (core dumped)
>
> or
>
> $ crash vmlinux vmcore
> ...
> Bus error (core dumped)
> $
>
> Gdb calltrace:
>
> $ gdb /home/lijiang/src/crash/crash /tmp/core.126301
> Core was generated by `./crash --osrelease /home/lijiang/src/39317/vmcore'.
> Program terminated with signal SIGBUS, Bus error.
> #0 __memcpy_evex_unaligned_erms () at ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:831
> 831 LOAD_ONE_SET((%rsi), PAGE_SIZE, %VMM(4), %VMM(5), %VMM(6), %VMM(7))
> (gdb) bt
> #0 __memcpy_evex_unaligned_erms () at ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:831
> #1 0x0000000000651096 in read_dump_header (file=0x7ffc59ddff5f "/home/lijiang/src/39317/vmcore") at diskdump.c:820
> #2 0x0000000000651cf3 in is_diskdump (file=0x7ffc59ddff5f "/home/lijiang/src/39317/vmcore") at diskdump.c:1042
> #3 0x0000000000502ac9 in get_osrelease (dumpfile=0x7ffc59ddff5f "/home/lijiang/src/39317/vmcore") at main.c:1938
> #4 0x00000000004fb2e8 in main (argc=3, argv=0x7ffc59dde3a8) at main.c:271
> (gdb) frame 1
> #1 0x0000000000651096 in read_dump_header (file=0x7ffc59ddff5f "/home/lijiang/src/39317/vmcore") at diskdump.c:820
> 820 memcpy(dd->dumpable_bitmap, dd->bitmap + bitmap_len/2,
>
> This may happen on attempting access to a page of the buffer that lies
> beyond the end of the mapped file(see the mmap() man page).
>
> Let's add a check to avoid such issues as much as possible, but still
> not guarantee that it can work well in any extreme situation.
>
> Fixes: a3344239743b ("diskdump: use mmap/madvise to improve the start-up")
> Reported-by: Buland Kumar Singh <bsingh@xxxxxxxxxx>
> Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
> ---
> diskdump.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/diskdump.c b/diskdump.c
> index 1f7118cacfc6..ce3cbb7b12dd 100644
> --- a/diskdump.c
> +++ b/diskdump.c
> @@ -805,6 +805,22 @@ restart:
> goto err;
> }
> } else {
> + struct stat sbuf;
> + if (fstat(dd->dfd, &sbuf) != 0) {
> + error(INFO, "Cannot fstat the dump file\n");
> + goto err;
> + }
> +
> + /*
> + * For memory regions mapped with the mmap(), attempts access to
> + * a page of the buffer that lies beyond the end of the mapped file,
> + * which may cause SIGBUS(see the mmap() man page).
> + */
> + if (bitmap_len + offset > sbuf.st_size) {
> + error(INFO, "Mmap: Beyond the end of mapped file, corrupted?\n");
> + goto err;
> + }
> +
> dd->bitmap = mmap(NULL, bitmap_len, PROT_READ,
> MAP_SHARED, dd->dfd, offset);
> if (dd->bitmap == MAP_FAILED)
> --
> 2.45.1
> --
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