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Hi Lianbo,
> -----Original Message-----
> From: crash-utility-bounces@redhat.com <crash-utility-bounces@redhat.com> On Behalf Of lijiang
> Sent: Monday, December 21, 2020 11:42 PM
> To: crash-utility@redhat.com; zhaoqianli@xiaomi.com
> Subject: Re: [Crash-utility] [PATCH V2] netdump: fix regression for tiny kdump files
>
> Hi, Qianli
>
> Thanks for the patch.
> 在 2020年12月01日 14:45, crash-utility-request@redhat.com 写道:
> > Date: Tue, 1 Dec 2020 10:56:02 +0800
> > From: Qianli Zhao <zhaoqianligood@gmail.com>
> > To: crash-utility@redhat.com, minipli@grsecurity.net
> > Subject: [Crash-utility] [PATCH V2] netdump: fix regression for tiny
> > kdump files
> > Message-ID:
> > <1606791362-5604-1-git-send-email-zhaoqianligood@gmail.com>
> > Content-Type: text/plain; charset="US-ASCII"
> >
> > From: Qianli Zhao <zhaoqianli@xiaomi.com>
> >
> > Commit f42db6a33f0e ("Support core files with "unusual" layout")
> > increased the minimal file size from MIN_NETDUMP_ELF_HEADER_SIZE to
> > SAFE_NETDUMP_ELF_HEADER_SIZE which lead to crash rejecting very
> > small kdump files.
> >
> Good findings.
>
> > Fix that by erroring out only if we get less than
> > MIN_NETDUMP_ELF_HEADER_SIZE bytes.
> >
> > Signed-off-by: Qianli Zhao <zhaoqianli@xiaomi.com>
> > ---
> > - Update commit message
> > - Add more accurate judgment of read() return value
> > ---
> > netdump.c | 9 +++++++--
> > 1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/netdump.c b/netdump.c
> > index c76d9dd..9a36931 100644
> > --- a/netdump.c
> > +++ b/netdump.c
> > @@ -119,7 +119,8 @@ is_netdump(char *file, ulong source_query)
> > Elf64_Phdr *load64;
> > char *eheader, *sect0;
> > char buf[BUFSIZE];
> > - size_t size, len, tot;
> > + ssize_t size;
> > + size_t len, tot;
> > Elf32_Off offset32;
> > Elf64_Off offset64;
> > ulong format;
> > @@ -142,10 +143,14 @@ is_netdump(char *file, ulong source_query)
> > if (!read_flattened_format(fd, 0, eheader, size))
> > goto bailout;
> > } else {
> > - if (read(fd, eheader, size) != size) {
> > + size = read(fd, eheader, size);
> > + if (size < 0) {
> > sprintf(buf, "%s: ELF header read", file);
> > perror(buf);
> > goto bailout;
> > + } else if (size < MIN_NETDUMP_ELF_HEADER_SIZE) {
>
> For the checking condition, I would recommend using the following methods, what do you think?
>
> + if (size != SAFE_NETDUMP_ELF_HEADER_SIZE &&
> + size != MIN_NETDUMP_ELF_HEADER_SIZE) {
> sprintf(buf, "%s: ELF header read", file);
> perror(buf);
> goto bailout;
> }
Do you mean putting "size < 0" and "size < MIN_NETDUMP_ELF_HEADER SIZE"
together? I think it would be good to separate an read error and a format
error for better debugging.
And according to ramdump_to_elf(), the size of an ELF header from a RAM
dumpfile varies depending on the number of nodes, and is equal to or more
than MIN_NETDUMP_ELF_HEADER_SIZE if valid. Actually, the value that Qianli
showed before was 232 [1], which is not either SAFE_NETDUMP_ELF_HEADER_SIZE(304)
or MIN_NETDUMP_ELF_HEADER_SIZE(176).
[1]
https://www.redhat.com/archives/crash-utility/2020-November/msg00080.html
Thanks,
Kazu
>
>
> In addition, would you mind updating another error output in the is_netdump()? For example:
>
> size = SAFE_NETDUMP_ELF_HEADER_SIZE;
> if ((eheader = (char *)malloc(size)) == NULL) {
> - fprintf(stderr, "cannot malloc minimum ELF header buffer\n");
> + fprintf(stderr, "cannot malloc ELF header buffer\n");
> clean_exit(1);
> }
>
> Thanks.
> Lianbo
>
> > + fprintf(stderr, "%s: file too small!\n", file);
> > + goto bailout;
> > }
> > }
> >
> > -- 2.7.4
>
> --
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