On 02/02/2017 02:04 AM, Yann Ylavic wrote:
Hi Niklas,
On Wed, Feb 1, 2017 at 7:02 PM, Niklas Edmundsson <[email protected]> wrote:
We've started to see spurious segfaults with httpd 2.4.25, mpm_event, ssl on
Ubuntu 14.04LTS. Not frequent, but none the less happening.
#4 ssl_io_filter_output (f=0x7f507013cfe0, bb=0x7f4f840be168) at
ssl_engine_io.c:1746
data = 0x7f5075518000 <error: Cannot access memory at address
0x7f5075518000>
len = 4194304
bucket = 0x7f4f840b1ba8
status = <optimized out>
filter_ctx = 0x7f507013cf88
inctx = <optimized out>
outctx = 0x7f507013d008
rblock = APR_NONBLOCK_READ
Idle thoughts: "Cannot access memory" in this case could be a red
herring, if Niklas' gdb can't peer into mmap'd memory spaces [1]. It
seems reasonable that the data in question could be mmap'd, given the
nice round address and 4 MiB length (equal to APR_MMAP_LIMIT).
That doesn't mean we're looking in the wrong place, though, since SIGBUS
can also be generated by an out-of-bounds access to an mmap'd region.
Niklas, what version of APR are you using? Are you serving large (> 4
MiB) static files? I have not been able to reproduce so far (Ubuntu
16.04, httpd 2.4.25 + mod_ssl + mpm_event).
--Jacob
[1]
https://stackoverflow.com/questions/654393/examining-mmaped-addresses-using-gdb
