Messages in this thread | | | From | Omar Sandoval <> | Subject | [PATCH RESEND 0/2] fix RLIMIT_CORE accounting for sparse dumps | Date | Fri, 1 Apr 2016 11:45:14 -0700 |
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From: Omar Sandoval <osandov@fb.com>
Resending this since it didn't get in -rc1. Rebased on Linus' current tree. Please apply.
Original cover letter below:
Hi,
Someone here reported that they were getting truncated core dumps even when RLIMIT_CORE was larger than the physical memory of the machine. It looks some cleanup patches back in v3.13 [1] changed the behaviour of the limit to also charge for sparse areas of a file. Here's an example in 4.5-rc4, where a.out is:
---- #include <signal.h>
int main(int argc, char **argv) { raise(SIGQUIT); return 0; } ----
Make sure that your sysctl kernel.core_pattern isn't piping anywhere, and be aware that there's some stupidity about the units used for ulimit -c in different shells (bash uses 1024-byte blocks, same as what's shown by du by default).
---- # ulimit -c unlimited # ./a.out Quit (core dumped) # du core.248 88 core.248 # du --apparent-size core.248 232 core.248 # ulimit -c 128 # ./a.out Quit (core dumped) # du core.252 64 core.252 # du --apparent-size core.252 72 core.252 ----
These 2 patches restore the original behavior:
---- # ulimit -c 128 # ./a.out Quit (core dumped) # du core.245 88 core.245 # du --apparent-size core.245 232 core.245 ----
Patch 1 gets rid of cprm->written, since as far as I could tell, it's always going to be equal to cprm->file->f_pos. Patch 2 reintroduces cprm->written as the number of bytes actually written to the file, not including what we seek over.
This series is based on 4.5-rc4. Al, could you apply these?
Thanks!
1: http://lkml.iu.edu/hypermail/linux/kernel/1310.1/00758.html
Appendix A: a quick sanity test with the patches applied
---- # ulimit -c unlimited # python -c 'import os, signal; l = [0] * 1024 * 1024; os.kill(os.getpid(), signal.SIGQUIT)' Quit (core dumped) # du core.262 12268 core.262 # du --apparent-size core.262 12628 core.262 # ulimit -c 1024 # python -c 'import os, signal; l = [0] * 1024 * 1024; os.kill(os.getpid(), signal.SIGQUIT)' Quit (core dumped) # du core.266 1024 core.266 # du --apparent-size core.266 1024 core.266 ----
Omar Sandoval (2): coredump: get rid of coredump_params->written coredump: only charge written data against RLIMIT_CORE
arch/powerpc/platforms/cell/spufs/coredump.c | 5 +++-- fs/binfmt_elf.c | 2 +- fs/binfmt_elf_fdpic.c | 2 +- fs/coredump.c | 7 ++----- 4 files changed, 7 insertions(+), 9 deletions(-)
-- 2.8.0
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