fix RLIMIT_CORE accounting for sparse dumps
Subsystems (5)
v3 cover fix RLIMIT_CORE accounting for sparse dumps
From: Omar Sandoval <[email protected]>
Ugh, and this time I forgot the Signed-off-by... Cover letter from v2 below:
Hi, Al,
I'm resending these patches because I realized that I made a subtle typo in my first version. I only just noticed that I inadvertently changed this in dump_emit().
----
- cprm->written += n;
+ cprm->written += nr;
----
That's fixed now, this applies to v4.6-rc3. Please apply or let me know if there's anything else I messed up.
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:
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# 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 | 5 +---- 4 files changed, 6 insertions(+), 8 deletions(-)
Signature · 1 line
2.8.0
PATCH v3 1/2 coredump: get rid of coredump_params->written
From: Omar Sandoval <[email protected]>
cprm->written is redundant with cprm->file->f_pos, so use that instead.
--- arch/powerpc/platforms/cell/spufs/coredump.c | 5 +++-- fs/binfmt_elf.c | 2 +- fs/binfmt_elf_fdpic.c | 2 +- fs/coredump.c | 8 +++----- include/linux/binfmts.h | 1 - 5 files changed, 8 insertions(+), 10 deletions(-)
arch/powerpc/platforms/cell/spufs/coredump.c +3 -2
@@ -137,6 +137,7 @@ static int spufs_arch_write_note(struct spu_context *ctx, int i,char *name;char fullname[80 ], *buf;struct elf_note en; +size_t skip; buf = (void *)get_zeroed_page (GFP_KERNEL );if (!buf)
@@ -171,8 +172,8 @@ static int spufs_arch_write_note(struct spu_context *ctx, int i,if (rc <0 ) goto out; -if (!dump_skip (cprm, -roundup (cprm->written - total + sz,4 ) - cprm->written)) + skip =roundup (cprm->file->f_pos - total + sz,4 ) - cprm->file->f_pos; +if (!dump_skip (cprm, skip)) goto Eio; out:free_page ((unsigned long )buf);
fs/binfmt_elf.c +1 -1
@@ -2273,7 +2273,7 @@ static int elf_core_dump(struct coredump_params *cprm) goto end_coredump;/* Align to page */ -if (!dump_skip (cprm, dataoff - cprm->written)) +if (!dump_skip (cprm, dataoff - cprm->file->f_pos)) goto end_coredump; for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
fs/binfmt_elf_fdpic.c +1 -1
@@ -1787,7 +1787,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm) goto end_coredump; } -if (!dump_skip (cprm, dataoff - cprm->written)) +if (!dump_skip (cprm, dataoff - cprm->file->f_pos)) goto end_coredump;if (!elf_fdpic_dump_segments (cprm))
fs/coredump.c +3 -5
@@ -782,7 +782,7 @@ int dump_emit(struct coredump_params *cprm, const void *addr, int nr)struct file *file = cprm->file;loff_t pos = file->f_pos;ssize_t n; -if (cprm->written + nr > cprm->limit) +if (pos + nr > cprm->limit)return 0 ;while (nr) {if (dump_interrupted ())
@@ -791,7 +791,6 @@ int dump_emit(struct coredump_params *cprm, const void *addr, int nr)if (n <=0 )return 0 ; file->f_pos = pos; - cprm->written += n; nr -= n; }return 1 ;
@@ -803,12 +802,11 @@ int dump_skip(struct coredump_params *cprm, size_t nr)static char zeroes[PAGE_SIZE ];struct file *file = cprm->file;if (file->f_op->llseek && file->f_op->llseek != no_llseek) { -if (cprm->written + nr > cprm->limit) +if (file->f_pos + nr > cprm->limit)return 0 ;if (dump_interrupted () || file->f_op->llseek (file, nr,SEEK_CUR ) <0 )return 0 ; - cprm->written += nr;return 1 ; }else {while (nr >PAGE_SIZE ) {
@@ -823,7 +821,7 @@ EXPORT_SYMBOL(dump_skip);int dump_align (struct coredump_params *cprm,int align) { -unsigned mod = cprm->written & (align -1 ); +unsigned mod = cprm->file->f_pos & (align -1 );if (align & (align -1 ))return 0 ;return mod ?dump_skip (cprm, align - mod) :1 ;
include/linux/binfmts.h +0 -1
@@ -64,7 +64,6 @@ struct coredump_params {struct file *file;unsigned long limit;unsigned long mm_flags; -loff_t written; };/*
Signature · 1 line
2.8.0
PATCH v3 2/2 coredump: only charge written data against RLIMIT_CORE
In reply to Omar SandovalFrom: Omar Sandoval <[email protected]>
Commit 9b56d54380ad ("dump_skip(): dump_seek() replacement taking coredump_params") introduced a regression with regard to RLIMIT_CORE. Previously, when a core dump was sparse, only the data that was actually written out would count against the limit. Now, the sparse ranges are also included, which leads to truncated core dumps when the actual disk usage is still well below the limit. Restore the old behavior by only counting what gets emitted and ignoring what gets skipped.
--- fs/coredump.c | 5 ++--- include/linux/binfmts.h | 1 + 2 files changed, 3 insertions(+), 3 deletions(-)
fs/coredump.c +2 -3
@@ -782,7 +782,7 @@ int dump_emit(struct coredump_params *cprm, const void *addr, int nr)struct file *file = cprm->file;loff_t pos = file->f_pos;ssize_t n; -if (pos + nr > cprm->limit) +if (cprm->written + nr > cprm->limit)return 0 ;while (nr) {if (dump_interrupted ())
@@ -791,6 +791,7 @@ int dump_emit(struct coredump_params *cprm, const void *addr, int nr)if (n <=0 )return 0 ; file->f_pos = pos; + cprm->written += n; nr -= n; }return 1 ;
@@ -802,8 +803,6 @@ int dump_skip(struct coredump_params *cprm, size_t nr)static char zeroes[PAGE_SIZE ];struct file *file = cprm->file;if (file->f_op->llseek && file->f_op->llseek != no_llseek) { -if (file->f_pos + nr > cprm->limit) -return 0 ;if (dump_interrupted () || file->f_op->llseek (file, nr,SEEK_CUR ) <0 )return 0 ;
include/linux/binfmts.h +1 -0
@@ -64,6 +64,7 @@ struct coredump_params {struct file *file;unsigned long limit;unsigned long mm_flags; +loff_t written; };/*
Signature · 1 line
2.8.0