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Avoid leaking duplicated file descriptors in corner cases.

Browse source 
pg_dump's compression modules had variations on the theme of

	fp = fdopen(dup(fd), mode);
	if (fp == NULL)
	    // fail, reporting errno

which is problematic for two reasons.  First, if dup() succeeds but
fdopen() fails, we'd leak the duplicated FD.  That's not important
at present since the program will just exit immediately after failure
anyway; but perhaps someday we'll try to continue, making the resource
leak potentially significant.  Second, if dup() fails then fdopen()
will overwrite the useful errno (perhaps EMFILE) with a misleading
value EBADF, making it difficult to understand what went wrong.
Fix both issues by testing for dup() failure before proceeding to
the next call.

These failures are sufficiently unlikely, and the consequences minor
enough, that this doesn't seem worth the effort to back-patch.
But let's fix it in HEAD.

Author: Jianghua Yang <yjhjstz@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/62bbe34d-2315-4b42-b768-56d901aa83e1@gmail.com
This commit is contained in:
Tom Lane 2026-03-19 14:25:26 -04:00
parent dd1398f137
commit 8b02c22bb4
4 changed files with 80 additions and 23 deletions
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22
src/bin/pg_dump/compress_gzip.c
View file

@ -386,12 +386,24 @@ Gzip_open(const char *path, int fd, const char *mode, CompressFileHandle *CFH)
strcpy(mode_compression, mode);
if (fd >= 0)
gzfp = gzdopen(dup(fd), mode_compression);
else
gzfp = gzopen(path, mode_compression);
{
int dup_fd = dup(fd);
if (gzfp == NULL)
return false;
if (dup_fd < 0)
return false;
gzfp = gzdopen(dup_fd, mode_compression);
if (gzfp == NULL)
{
close(dup_fd);
return false;
}
}
else
{
gzfp = gzopen(path, mode_compression);
if (gzfp == NULL)
return false;
}
CFH->private_data = gzfp;

29
src/bin/pg_dump/compress_lz4.c
View file

@ -715,13 +715,30 @@ LZ4Stream_open(const char *path, int fd, const char *mode,
LZ4State *state = (LZ4State *) CFH->private_data;
if (fd >= 0)
state->fp = fdopen(dup(fd), mode);
else
state->fp = fopen(path, mode);
if (state->fp == NULL)
{
state->errcode = errno;
return false;
int dup_fd = dup(fd);
if (dup_fd < 0)
{
state->errcode = errno;
return false;
}
state->fp = fdopen(dup_fd, mode);
if (state->fp == NULL)
{
state->errcode = errno;
close(dup_fd);
return false;
}
}
else
{
state->fp = fopen(path, mode);
if (state->fp == NULL)
{
state->errcode = errno;
return false;
}
}
return true;

22
src/bin/pg_dump/compress_none.c
View file

@ -231,12 +231,24 @@ open_none(const char *path, int fd, const char *mode, CompressFileHandle *CFH)
Assert(CFH->private_data == NULL);
if (fd >= 0)
CFH->private_data = fdopen(dup(fd), mode);
else
CFH->private_data = fopen(path, mode);
{
int dup_fd = dup(fd);
if (CFH->private_data == NULL)
return false;
if (dup_fd < 0)
return false;
CFH->private_data = fdopen(dup_fd, mode);
if (CFH->private_data == NULL)
{
close(dup_fd);
return false;
}
}
else
{
CFH->private_data = fopen(path, mode);
if (CFH->private_data == NULL)
return false;
}
return true;
}

30
src/bin/pg_dump/compress_zstd.c
View file

@ -523,14 +523,30 @@ Zstd_open(const char *path, int fd, const char *mode,
}
if (fd >= 0)
fp = fdopen(dup(fd), mode);
else
fp = fopen(path, mode);
if (fp == NULL)
{
pg_free(zstdcs);
return false;
int dup_fd = dup(fd);
if (dup_fd < 0)
{
pg_free(zstdcs);
return false;
}
fp = fdopen(dup_fd, mode);
if (fp == NULL)
{
close(dup_fd);
pg_free(zstdcs);
return false;
}
}
else
{
fp = fopen(path, mode);
if (fp == NULL)
{
pg_free(zstdcs);
return false;
}
}
zstdcs->fp = fp;