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* [Bug dynamic-link/26322] New: Libraries may fail to load if (p)read doesn't return all bytes requested
@ 2020-07-30 18:04 jasonwhite at fb dot com
2020-08-03 18:00 ` [Bug dynamic-link/26322] " carlos at redhat dot com
2020-08-03 18:00 ` carlos at redhat dot com
0 siblings, 2 replies; 3+ messages in thread
From: jasonwhite at fb dot com @ 2020-07-30 18:04 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=26322
Bug ID: 26322
Summary: Libraries may fail to load if (p)read doesn't return
all bytes requested
Product: glibc
Version: 2.33
Status: UNCONFIRMED
Severity: minor
Priority: P2
Component: dynamic-link
Assignee: unassigned at sourceware dot org
Reporter: jasonwhite at fb dot com
Target Milestone: ---
In `elf/dl-load.c` there is a call to pread[1]:
if ((size_t) __pread64_nocancel (fd, (void *) phdr, maplength,
ehdr->e_phoff) != maplength)
{
read_error:
errval = errno;
errstring = N_("cannot read file data");
goto call_lose;
}
However, there is no guarantee that pread will return all the bytes requested.
Thus, I believe the read should be wrapped in a loop to ensure it receives all
the bytes requested.
I found this issue while simulating a pathological kernel that only returns one
byte at a time for read calls using ptrace. I imagine this could also be
reproduced by writing a small FUSE file system that only returns a byte at a
time for reads.
[1]:
https://sourceware.org/git/?p=glibc.git;a=blob;f=elf/dl-load.c;h=c1bc8c26be1229fafc2a03afd9fb27edbcf8c3a8;hb=95c1056962a3f2297c94ce47f0eaf0c5b6563231#l1667
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* [Bug dynamic-link/26322] Libraries may fail to load if (p)read doesn't return all bytes requested
2020-07-30 18:04 [Bug dynamic-link/26322] New: Libraries may fail to load if (p)read doesn't return all bytes requested jasonwhite at fb dot com
@ 2020-08-03 18:00 ` carlos at redhat dot com
2020-08-03 18:00 ` carlos at redhat dot com
1 sibling, 0 replies; 3+ messages in thread
From: carlos at redhat dot com @ 2020-08-03 18:00 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=26322
Carlos O'Donell <carlos at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |carlos at redhat dot com
--- Comment #1 from Carlos O'Donell <carlos at redhat dot com> ---
(In reply to Jason White from comment #0)
> I found this issue while simulating a pathological kernel that only returns
> one byte at a time for read calls using ptrace. I imagine this could also be
> reproduced by writing a small FUSE file system that only returns a byte at a
> time for reads.
Thanks for the report. There are probably a few places where we require the
read of a given length to succeed. You are right though, we should look into
this and either document the requirement or fix the issue.
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* [Bug dynamic-link/26322] Libraries may fail to load if (p)read doesn't return all bytes requested
2020-07-30 18:04 [Bug dynamic-link/26322] New: Libraries may fail to load if (p)read doesn't return all bytes requested jasonwhite at fb dot com
2020-08-03 18:00 ` [Bug dynamic-link/26322] " carlos at redhat dot com
@ 2020-08-03 18:00 ` carlos at redhat dot com
1 sibling, 0 replies; 3+ messages in thread
From: carlos at redhat dot com @ 2020-08-03 18:00 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=26322
Carlos O'Donell <carlos at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2020-08-03
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2020-07-30 18:04 [Bug dynamic-link/26322] New: Libraries may fail to load if (p)read doesn't return all bytes requested jasonwhite at fb dot com
2020-08-03 18:00 ` [Bug dynamic-link/26322] " carlos at redhat dot com
2020-08-03 18:00 ` carlos at redhat dot com
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