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readLink(): Handle symlinks in /proc

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Symlinks like /proc/self/exe report a stat() size of 0, so use a
buffer of at least PATH_MAX instead.
This commit is contained in:
Eelco Dolstra 2017-08-29 11:51:16 +02:00
parent 2cc345b95f
commit 05c45f301d
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GPG key ID: 8170B4726D7198DE
1 changed files with 5 additions and 4 deletions
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9
src/libutil/util.cc
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@ -219,13 +219,14 @@ Path readLink(const Path & path)
struct stat st = lstat(path); struct stat st = lstat(path);
if (!S_ISLNK(st.st_mode)) if (!S_ISLNK(st.st_mode))
throw Error(format("'%1%' is not a symlink") % path); throw Error(format("'%1%' is not a symlink") % path);
char buf[st.st_size]; auto bufSize = std::max(st.st_size, (off_t) PATH_MAX + 1);
ssize_t rlsize = readlink(path.c_str(), buf, st.st_size); char buf[bufSize];
ssize_t rlsize = readlink(path.c_str(), buf, bufSize);
if (rlsize == -1) if (rlsize == -1)
throw SysError(format("reading symbolic link '%1%'") % path); throw SysError(format("reading symbolic link '%1%'") % path);
else if (rlsize > st.st_size) else if (rlsize > bufSize)
throw Error(format("symbolic link '%1%' size overflow %2% > %3%") throw Error(format("symbolic link '%1%' size overflow %2% > %3%")
% path % rlsize % st.st_size); % path % rlsize % bufSize);
return string(buf, rlsize); return string(buf, rlsize);
} }